Styrene-free coating compositions for packaging articles such as food and beverage containers

ABSTRACT

A method of forming a coating on a food or beverage container, which includes spraying a coating composition onto an interior surface of the food or beverage container, where the coating composition includes an emulsion-polymerized latex copolymer having copolymer chains of one or more ethylenically-unsaturated monomers and one or more styrene offset monomers. Preferably, the coating composition is substantially free of BPA, PVC, and styrene. The method may also include curing the sprayed coating composition, thereby providing the coating on the interior surface of the food or beverage container.

CROSS REFERENCE TO RELATED APPLICATION

This application is a national stage filing under 35 U.S.C. § 371 ofInternational Application No. PCT/US2015/000236 filed on Dec. 23, 2015,which claims the benefit of U.S. provisional application No. 62/096,573filed on Dec. 24, 2014 and entitled “STYRENE-FREE COATING COMPOSITIONSFOR PACKAGING ARTICLES SUCH AS FOOD AND BEVERAGE CONTAINERS”, thedisclosures of which are incorporated herein by reference in its theirentirety.

FIELD

The present disclosure is directed to coating compositions. Inparticular, the present disclosure is directed to latex emulsion coatingcompositions, such as for forming coatings (e.g., spray coatings) forfood and beverage containers, as well as other packaging articles.

BACKGROUND

A wide variety of coatings have been used to coat the surfaces ofpackaging articles (e.g., food and beverage cans). For example, metalcans are sometimes coated using “coil coating” or “sheet coating”operations, i.e., a planar coil or sheet of a suitable substrate (e.g.,steel or aluminum metal) is coated with a suitable composition andhardened (e.g., cured). The coated substrate then is formed into the canend or body. Alternatively, liquid coating compositions may be applied(e.g., by spraying, dipping, rolling, etc.) to the formed or partiallyformed article and then hardened (e.g., cured).

Packaging coatings should preferably be capable of high-speedapplication to the substrate and provide the necessary properties whenhardened to perform in this demanding end use. For example, the coatingshould be safe for food contact, have excellent adhesion to thesubstrate, have sufficient flexibility to withstand deflection of theunderlying substrate without rupturing (e.g., during fabrication stepsand/or damage occurring during transport or use of the packagingarticle), and resist degradation over long periods of time, even whenexposed to harsh environments.

Many current packaging coatings contain mobile or bound bisphenol A(“BPA”) or aromatic glycidyl ether compounds, polyvinyl chloride(“PVC”), or styrene. Although the balance of scientific evidenceavailable to date indicates that the small trace amounts of thesecompounds that might be released from existing coatings does not poseany health risks to humans, these compounds are nevertheless perceivedby some people as being potentially harmful to human health. From theforegoing, it will be appreciated that what is needed in the art is apackaging container (e.g., a food or beverage can or a portion thereof)that is coated with a composition that does not contain extractablequantities of such compounds.

SUMMARY

An aspect of the present disclosure is directed to a method of forming acoating on a packaging article, such as a food or beverage container.The method includes applying a coating composition using any suitabletechnique to a substrate (typically a metal substrate) prior to or afterforming the substrate into a food or beverage container or a portionthereof. The coating composition may be used to form either an exteriorcoating or an interior coating.

In a preferred embodiment, the coating composition is spray applied ontoan interior surface of a food or beverage container. The coatingcomposition includes an emulsion-polymerized latex copolymer dispersedin an aqueous carrier, where the latex copolymer is preferably areaction product of monomers that include one or moreethylenically-unsaturated monomers and one or more styrene offsetmonomers, where, in preferred embodiments, the monomers used to producethe latex copolymer are substantially free of BPA, PVC and otherhalogenated monomers, and styrene. In some further preferredembodiments, the monomers used to produce the latex copolymer aresubstantially free of oxirane groups.

The styrene offset monomers preferably include (i) anethylenically-unsaturated monomer having a polycyclic group, (ii) anethylenically-unsaturated monomer having a monocyclic group with a ringstructure having 3-5 atoms in the ring, or (iii) combinations thereof,where a combined concentration of (i) and (ii) preferably constitutes atleast about 10% by weight of the monomers used to produce theemulsion-polymerized latex copolymer. In some embodiments, the styreneoffset monomers include one or more of the above monomers (i) and (ii)in combination with an ethylenically-unsaturated monomer, other thanstyrene, having a monocyclic group with 6 or more atoms in the ring(e.g., benzyl (meth)acrylate and/or cyclohexyl (meth)acrylate).

Definitions

Unless otherwise specified, the following terms as used herein have themeanings provided below:

The terms “preferred” and “preferably” refer to embodiments of theinvention that may afford certain benefits, under certain circumstances.However, other embodiments may also be preferred, under the same orother circumstances. Furthermore, the recitation of one or morepreferred embodiments does not imply that other embodiments are notuseful, and is not intended to exclude other embodiments from the scopeof the present disclosure.

The term “about” is used herein with respect to measurable values andranges due to expected variations known to those skilled in the art(e.g., limitations and variabilities in measurements).

The term “organic group” means a hydrocarbon group (with optionalelements other than carbon and hydrogen, such as oxygen, nitrogen,sulfur, and silicon) that is classified as an aliphatic group, a cyclicgroup, or combination of aliphatic and cyclic groups (e.g., alkaryl andaralkyl groups).

The term “aryl group” (e.g., an arylene group) refers to a closedaromatic ring or ring system such as phenylene, naphthylene,biphenylene, fluorenylene, and indenyl, as well as heteroarylene groups(i.e., a closed aromatic or aromatic-like ring hydrocarbon or ringsystem in which one or more of the atoms in the ring is an element otherthan carbon (e.g., nitrogen, oxygen, sulfur, etc.)). Suitable heteroarylgroups include furyl, thienyl, pyridyl, quinolinyl, isoquinolinyl,indolyl, isoindolyl, triazolyl, pyrrolyl, tetrazolyl, imidazolyl,pyrazolyl, oxazolyl, thiazolyl, benzofuranyl, benzothiophenyl,carbazolyl, benzoxazolyl, pyrimidinyl, benzimidazolyl, quinoxalinyl,benzothiazolyl, naphthyridinyl, isoxazolyl, isothiazolyl, purinyl,quinazolinyl, pyrazinyl, 1-oxidopyridyl, pyridazinyl, triazinyl,tetrazinyl, oxadiazolyl, thiadiazolyl, and so on. When such groups aredivalent, they are typically referred to as “arylene” or “heteroarylene”groups (e.g., furylene, pyridylene, etc.).

The term “ethylenically-unsaturated group” refers to a carbon-carbondouble or triple bond capable of participating in a free-radicalinitiated emulsion polymerization reaction, and is not intended toencompass the carbon-carbon double bonds present in aryl groups such as,for example, the phenyl group of styrene.

The term “cyclic group” means a closed ring organic group that isclassified as an alicyclic group or an aromatic group, both of which caninclude heteroatoms.

The term “alicyclic group” means a cyclic organic group havingproperties resembling those of aliphatic groups.

The term “polycyclic” when used in the context of a group refers to anorganic group that includes at least two cyclic groups in which one ormore atoms (and more typically two or more atoms) are present in therings of both of the at least two cyclic groups. Thus, for example, agroup that consists of two cyclohexane groups connected by a singlemethlylene group is not a polycyclic group.

The term “tricyclic” group refers to a polycyclic group that includesthree cyclic groups in which the ring of each cyclic group shares one ormore atoms with one or both of the rings of the other cyclic groups.

A group that may be the same or different is referred to as being“independently” something.

Substitution is anticipated on the organic groups of the compounds ofthe present invention. As a means of simplifying the discussion andrecitation of certain terminology used throughout this application, theterms “group” and “moiety” are used to differentiate between chemicalspecies that allow for substitution or that may be substituted and thosethat do not allow or may not be so substituted. Thus, when the term“group” is used to describe a chemical substituent, the describedchemical material includes the unsubstituted group and that group withO, N, Si, or S atoms, for example, in the chain (as in an alkoxy group)as well as carbonyl groups or other conventional substitution. Where theterm “moiety” is used to describe a chemical compound or substituent,only an unsubstituted chemical material is intended to be included. Forexample, the phrase “alkyl group” is intended to include not only pureopen chain saturated hydrocarbon alkyl substituents, such as methyl,ethyl, propyl, t-butyl, and the like, but also alkyl substituentsbearing further substituents known in the art, such as hydroxy, alkoxy,alkylsulfonyl, halogen atoms, cyano, nitro, amino, carboxyl, etc. Thus,“alkyl group” includes ether groups, haloalkyls, nitroalkyls,carboxyalkyls, hydroxyalkyls, sulfoalkyls, etc. On the other hand, thephrase “alkyl moiety” is limited to the inclusion of only pure openchain saturated hydrocarbon alkyl substituents, such as methyl, ethyl,propyl, t-butyl, and the like. As used herein, the term “group” isintended to be a recitation of both the particular moiety, as well as arecitation of the broader class of substituted and unsubstitutedstructures that includes the moiety.

The terms “a”, “an”, “the”, “at least one,” and “one or more” are usedinterchangeably. Thus, for example, reference to “a” chemical compoundrefers one or more molecules of the chemical compound, rather than beinglimited to a single molecule of the chemical compound. Furthermore, theone or more molecules may or may not be identical, so long as they fallunder the category of the chemical compound. Thus, for example, “a”polyester is interpreted to include one or more polymer molecules of thepolyester, where the polymer molecules may or may not be identical(e.g., different molecular weights, isomers, etc. . . . ).

The term “substantially free” of a particular compound means that thecompositions of the present disclosure contain less than 100 parts permillion (ppm) of the recited compound. The term “essentially free” of aparticular compound means that the compositions of the presentdisclosure contain less than 10 ppm of the recited compound. The term“essentially completely free” of a particular compound means that thecompositions of the present disclosure contain less than 1 ppm of therecited compound. The term “completely free” of a particular compoundmeans that the compositions of the present disclosure contain less than20 parts per billion (ppb) of the recited compound.

The term “food-contact surface” refers to the substrate surface of acontainer (typically an inner surface of a food or beverage container)that is in contact with, or intended for contact with, a food orbeverage product. By way of example, an interior surface of a metalsubstrate of a food or beverage container, or a portion thereof, is afood-contact surface even if the interior metal surface is coated with apolymeric coating composition.

The term “on,” when used in the context of a coating applied on asurface or substrate, includes both coatings applied directly orindirectly to the surface or substrate. Thus, for example, a coatingapplied to a primer layer overlying a substrate constitutes a coatingapplied on the substrate.

The term “polymer” includes both homopolymers and copolymers (e.g.,polymers of two or more different monomers). Similarly, unless otherwiseindicated, the use of a term designating a polymer class such as, forexample, “acrylic” is intended to include both homopolymers andcopolymers (e.g., polyester-acrylic copolymers).

The term “monomer” includes any reactant molecule used to produce apolymer, and encompasses both single-unit molecules (e.g., an acrylicmolecule) and multi-unit molecules (e.g., an acrylic oligomer).

The terms “comprises” and variations thereof do not have a limitingmeaning where these terms appear in the description and claims.

Also herein, the recitations of numerical ranges by endpoints includeall numbers subsumed within that range (e.g., 1 to 5 includes 1, 1.5, 2,2.75, 3, 3.80, 4, 5, etc.). Furthermore, disclosure of a range includesdisclosure of all subranges included within the broader range (e.g., 1to 5 discloses 1 to 4, 1.5 to 4.5, 1 to 2, etc.).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a two-piece food or beveragecontainer having a coating formed from the coating composition of thepresent disclosure.

FIG. 2 is a side view of an example spray coating process for sprayingthe coating composition of the present disclosure onto an interiorsurface of a can, such as a food or beverage can.

FIG. 3 is a top view of the example spray coating process shown in FIG.2.

DETAILED DESCRIPTION

The present disclosure is directed to a coating composition formulatedfrom a latex emulsion that, in preferred embodiments, is substantiallyfree or completely free of BPA, PVC and halogenated monomers, andstyrene, and has a suitable glass transition temperature (e.g., greaterthan about 40° C.) for reduced flavor scalping. As discussed below, thelatex emulsion is preferably produced from monomers that include one ormore “styrene-offset” monomers, which preferably contribute to higherglass transition temperatures and chemical resistance, and alsopreferably adhesion to metal substrates. As such, the coatingcomposition is particularly suitable for use in interior food-contactcoating applications, including spray coating applications to coatinterior surfaces of containers, including portions thereof, such as foruse in packaging food and beverage products.

The latex emulsion of the coating composition may include an aqueouscarrier and particles of a latex copolymer that is polymerized in one ormore emulsion polymerization steps. The latex emulsion may optionally befurther formulated and/or modified, such as, for example, forinside-spray coating applications. The resulting coating composition maythen be spray applied on an interior metal surface of a formed orpartially-formed container (e.g., a food or beverage container). Theapplied coating composition may then be cured on the interior metalsurface to produce a protective interior coating. Alternatively, thecoating composition may be applied on an interior or exterior surfaceusing any suitable coating technique (e.g., roll coating, wash coating,dip coating, etc.) prior to or after forming the substrate to be coatedinto a food or beverage container or a portion thereof.

During the emulsion polymerization to produce the latex copolymer,reactant monomers, may be dispersed or otherwise suspended in an aqueouscarrier, optionally with the use of one or more external surfactants.The reactant monomers may include a mixture of compounds capable ofpolymerizing under free radical-initiated, emulsion polymerizationconditions, such as monomers having ethylenically-unsaturated groups.

The reactant monomers preferably include one or moreethylenically-unsaturated monomers, where at least a portion of theethylenically-unsaturated monomers are styrene-offset monomers. As usedherein, “the total weight of the reactant monomers” refers to the totalweight of all monomers that are polymerized to produce the latexcopolymer with covalent bonds.

The ethylenically-unsaturated monomers may each include one or moreethylenically-unsaturated groups. This allows the monomers to polymerizewith each other to form copolymer chains, which may be linear and/orbranched. Additionally, in some embodiments, a portion of theethylenically-unsaturated monomers preferably have two or moreethylenically-unsaturated groups. These monomers may react to forminterconnecting linkages between the copolymer chains (or as growthsites for the copolymer chains), thereby crosslinking the copolymerchains. The collection of optional cross-linked polymer chains producethe latex copolymer, which can be provided as a copolymer particledispersed in the aqueous carrier.

Examples of suitable compounds for the ethylenically-unsaturatedmonomers include the styrene-offset monomers, (meth)acrylate monomers,ethylenically-unsaturated acid-functional monomers, polymerizablesurfactants, oligomers thereof, and mixtures thereof.

The styrene-offset monomers may include any ethylenically-unsaturatedcyclic monomer that preferably contribute to higher glass transitiontemperatures, chemical resistance, and/or adhesion to metal substrates.Suitable ethylenically-unsaturated cyclic monomers include non-styrenicmonomers having cyclic groups and ethylenically-unsaturated groups(e.g., cyclic vinyl monomers), such as one or moreethylenically-unsaturated aromatic monomers, ethylenically-unsaturatedalicyclic monomers, and mixtures thereof.

Illustrative ethylenically-unsaturated cyclic monomers include thoserespectively having the following structure:

where group R₁ may be a hydrogen atom or an organic group, such as aC₁-C₆ alkyl group, and more preferably a hydrogen atom or a methylgroup. Additionally, one or both of the hydrogen atoms attached to theterminal carbon atom of the ethylenically-unsaturated group may bereplaced with an independent group R₁. Group R₂ may be any suitableorganic group, such as, for example, a C₁-C₁₆ alkyl or alkenyl group,which can be substituted with one or more (e.g., 1-3) groups such ashydroxy group, halogen groups, oxirane groups, and alkoxy groups, forexample.

Group X may be a —COO— ester group, another step-growth linkage group, ahydrocarbyl group, a combination thereof, or may be omitted. Inpreferred embodiments, the ethylenically-unsaturated cyclic monomers arefree of oxirane groups or halogen groups, and more preferably both. Theinteger “n” may be zero or one, where, when “n” is zero, group R₂ isomitted and the —X-G_(Cyclic) group extends directly from theunsaturated group. In some preferred embodiments, when group G_(Cyclic)is an aromatic ring, Group X is a —COO— ester group and/or “n” is one,such that the aromatic ring does not directly extend from theethylenically-unsaturated group. In further preferred embodiments, theunsaturated bond (e.g., double bond) is connected to a terminal carbonof the molecule (e.g., a CH₂ group), as shown in Formula 1.

Group G_(Cyclic) may be any suitable group having one or more cyclicgroups, where at least a portion of the cyclic groups preferably do notreact during polymerization such that the cyclic group(s) remain as apendant and/or terminal group of the copolymer chain. For example, GroupG_(Cyclic) may include one or more C₃-C₁₀ ring structures, where one ormore of the carbon atoms in the ring structures may be substituted withother atoms, such as oxygen, nitrogen, nitrogen, silicon, sulfur,phosphorus, and the like. Furthermore, group G_(Cyclic) may also includeone or more additional groups that may extend from one or more atoms ofthe ring structures(s), such as one or more organic groups (e.g., C₁-C₁₆alkyl or alkenyl groups), hydroxy groups, halogen groups, oxiranegroups, and alkoxy groups, for example.

In some embodiments, Group G_(Cyclic) may include a monocyclic aromaticor alicyclic structure. In these embodiments, group G_(Cyclic) morepreferably includes a monocyclic alicyclic structure having C₃-C₁₀ ringstructures, where at least a portion of the styrene-offset monomers(e.g., >1%, >5%, >10%, >20%, >30%, >40%, >50%, >75%, >90%, >95%, etc.)preferably having C₃, C₄, or C₅ ring structures, or with substitutedatoms.

Examples of suitable monomers having monocyclic alicyclic structures mayinclude tetrahydrofurfuryl (meth)acrylate, furfuryl (meth)acrylate,cyclopropyl (meth)acrylate, cyclobutyl (meth)acrylate, cyclopentyl(meth)acrylate, cyclohexyl (meth)acrylate, substituted variants thereof(e.g., substitution of one or more hydrogen atoms, and especiallyhydrogen atom(s) attached to the alicyclic ring) and the like. Examplesof suitable monomers having monocyclic aromatic structures may includebenzyl (meth)acrylate, benzyl 2-ethyl acrylate,2-(4-Benzoyl-3-hydroxyphenoxy)ethyl acrylate, vinyl toluene, benzyl2-propylacrylate, substituted variants thereof, and the like.

In other embodiments, Group G_(Cyclic) may include a polycyclic group,which preferably includes two or more alicylic and/or aromatic rings,such as bicyclic groups, tricyclic groups, tetracyclic groups, and thelike, where adjacent rings may have fused, bridged, and/or spiroarrangements. In these embodiments, each ring structure more preferablyincludes a C₃-C₁₀ ring structure, where adjacent rings preferablycontain at least one common atom. In some further embodiments, adjacentrings of the polycyclic group contain at least two common atoms (e.g.,for fused and bridged rings). In some additional embodiments, adjacentrings of the polycyclic group contain at least three common atoms (e.g.,for bridged rings). In certain preferred embodiments, the polycyclicgroup includes two or more 5-atom rings, two or more 6-atom rings, or atleast one 5-atom ring and at least one 6-atom ring.

Specific examples of suitable polycyclic monomers for the styrene-offsetmonomers may include isobornyl (meth)acrylate), norbornane(meth)acrylate, norbornene (meth)acrylate, norbornadiene,tricyclodecenyl (meth)acrylate, isosorbide (metha)crylate,tricyclodecane (meth)acrylate, bicyclo[4.4.0]decane (meth)acrylate,vinyl variations thereof, and mixtures thereof.

In some embodiments, one or more polycyclic groups are derived fromplant based materials such as, for, example corn. Examples of suitableplant-based materials include compounds derived from sugars, withanhydrosugars being preferred, and dianhydrosugars being especiallypreferred. Examples of suitable such compounds include bisanhydrodexitolor isohexide compounds, such as isosorbide, isomannide, isoidide,derivatives thereof, and mixtures thereof.

In some embodiments, the one or more polycyclic groups are unsaturatedbicyclic groups represented by the IUPAC (International Union of Pureand Applied Chemistry) nomenclature of Formula 2 below:bicyclo[x.y.z]alkene  (Formula 2)where “x” is an integer having a value of 2 or more, “y” is an integerhaving a value of 1 or more, “z” is an integer having a value of 0 ormore, and the term alkene refers to the IUPAC nomenclature designation(e.g., hexene, heptene, heptadiene, octene, etc.) for a given bicyclicmolecule and denotes that that the bicyclic group includes one or moredouble bonds (more typically one or more carbon-carbon double bonds).

In some embodiments, “z” in Formula 2 is one or more. In other words, incertain embodiments, the bicyclic groups are bridged bicyclic groups. Byway of example, bicyclo[4.4.0]decane is not a bridged bicyclic. In someembodiments, “x” has a value of 2 or 3 (more preferably 2) and each of“y” and “z” independently have a value of 1 or 2. The bicyclicstructures represented by Formula 2 include one or more carbon-carbondouble bonds (e.g., 1, 2, 3, etc.).

Non-limiting examples of some suitable unsaturated bicyclic groupsrepresented by Formula 2 include bicyclo[2.1.1]hexene,bicyclo[2.2.1]heptene (i.e., norbornene), bicyclo[2.2.2]octene,bicyclo[2.2.1]heptadiene, and bicyclo[2.2.2]octadiene. It is alsocontemplated that the bicyclic groups represented by Formula 2 maycontain one or more heteroatoms (e.g., nitrogen, oxygen, sulfur, etc.)and may be substituted to contain one or more additional substituents.For example, one or more cyclic groups (including, e.g., pendant cyclicgroups and ring groups fused to a ring of a bicyclic group) or acyclicgroups may be attached to the bicyclic group represented by Formula 1.Thus, for example, in some embodiments the bicyclic group of Formula 1may be present in a tricyclic or higher group.

In some embodiments, some or all of the bicyclic groups may besaturated. Non-limiting examples of saturated bicyclics includesaturated homologs of the structures represented by Formula 2 (i.e.,bicyclo[x.y.z]alkane, with x, y, and z as previously described) such as,for example, bicyclo[2.1.1]hexane, bicyclo[2.2.1]heptane,bicyclo[2.2.2]octane, and bicyclo[3.2.1]octane, bicyclo[4.3.2]undecane,bicyclo[5.2.0]nonane. In one embodiment, the bicyclic group includes twosaturated spiro, fused, and/or bridged rings and further includes one ormore unsaturated and/or aromatic organic groups attached to one of thesaturated rings.

The styrene-offset monomers may constitute greater than about 5%, morepreferably greater than about 10%, even more preferably greater thanabout 20%, and even more preferably greater than about 30% by weight ofthe latex copolymer, based on the total weight of the reactant monomers.The styrene-offset monomers may also constitute less than about 90%,more preferably less than about 70%, even more preferably less thanabout 60%, and even more preferably less than about 50% by weight of thelatex copolymer, based on the total weight of the reactant monomers.Typically, a majority (>50 wt-%), a substantial majority (e.g., >70wt-%, >80 wt-%, >90 wt-%, etc.), or substantially all (e.g., >95wt-%, >99 wt-%, etc.) of the styrene-offset monomers are cyclic-groupcontaining monomers.

In preferred embodiments, a significant portion, or even all, of thestyrene-offset monomers(e.g., >5%, >10%, >20%, >30%, >40%, >50%, >75%, >90%, >95%, etc.) isobtained from (i) the polycyclic monomers and/or (ii) the monocyclicmonomers having ring structures with 3-5 atoms (e.g., C₃, C₄, or C₅ ringstructures, or with substituted atoms) (collectively referred to as the“preferred styrene-offset monomers”. For example, the preferredstyrene-offset monomers may constitute at least about 10%, morepreferably greater than about 20%, and even more preferably greater thanabout 30% by weight of the latex copolymer, based on the total weight ofthe reactant monomers.

In some embodiments, at least some of the styrene-offset monomers may benon-cyclic monomers that preferably contribute to a film having arelatively “high” glass transition temperature. Examples of suchmonomers may include ethylenically unsaturated monomers havinghomopolymers with glass transition temperatures >50° C., >60° C., >70°C., >80° C., or >90° C. Specific examples may include acrylonitrile (97°C.), acrylic acid (106° C.), methacrylic acid (228° C.), methylmethacrylate (105° C.), ethyl methacrylate (65° C.), isobutylmethacrylate (53° C.), 2 hydroxy ethyl methacrylate (55° C.), 2 hydroxypropyl methacrylate (55° C.), and acrylamide (165° C.), wherein a glasstransition temperature for a homopolymer of each monomer as recited inH. Coyard et al., Resins for Surface Coatings: Acrylics & Epoxies 40-41(PKT Oldring, ed.), Vol. 1 (2nd ed. 2001) is reported in parentheses.Methyl methacrylate is a preferred such monomer.

Suitable non-cyclic (meth)acrylate monomers for use in the latexcopolymer include those having the following structure:

where group R₃ may be a hydrogen atom or an organic group, such as aC₁-C₆ alkyl group, and more preferably a hydrogen atom or a methylgroup. Additionally, one or both of the hydrogen atoms attached to theterminal carbon atom of the ethylenically-unsaturated group may bereplaced with an independent group R₃. Groups R₄ and R₅ may eachindependently be any suitable organic group, such as, for example, aC₁-C₁₆ alkyl or alkenyl group, which can be substituted with one or more(e.g., 1-3) groups such as hydroxy group, halogen groups, phenyl groups,oxirane groups, and alkoxy groups, for example.

Group X in Formula 3 is a —COO— ester group. In preferred embodiments,the mono-unsaturated monomers are free of oxirane groups or halogengroups, and more preferably both. The integer “n” may be zero or one,more preferably zero such that group R₄ is omitted and the —X—R₅ groupextends directly from the unsaturated group. In further preferredembodiments, the unsaturated bond (e.g., double bond) is connected to aterminal carbon of the molecule (e.g., a CH₂ group), as shown in Formula3.

Specific examples of suitable non-cyclic (meth)acrylates encompass alkyl(meth)acrylates, which are preferably esters of acrylic or methacrylicacid. Examples of suitable alkyl (meth)acrylates include methyl(meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl(meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, pentyl(meth)acrylate, isoamyl (meth)acrylate, hexyl (meth)acrylate,2-ethylhexyl (meth)acrylate, decyl (meth)acrylate, isodecyl(meth)acrylate, lauryl (meth)acrylate, octyl (meth)acrylate, nonyl(meth)acrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate,hydroxypropyl (meth)acrylate, and mixtures thereof.

The one or more non-cyclic (meth)acrylate monomers may constitutegreater than about 10%, more preferably greater than about 20%, and evenmore preferably greater than about 30% by weight of the latex copolymer,based on the total weight of the reactant monomers. The non-cyclic(meth)acrylate monomers may also constitute less than about 70% or about80%, more preferably less than about 60%, and even more preferably lessthan about 50% by weight of the latex copolymer, based on the totalweight of the reactant monomers.

The above-discussed non-cyclic (meth)acrylate monomers refer to monomerseach having a single ethylenically-unsaturated group, allowing thesemonomers to be polymerized to produce monomer units of the copolymerchains for the latex copolymer. In addition, the reactant monomers mayalso include one or more monomers each having two or moreethylenically-unsaturated groups (referred to as “multi-unsaturatedmonomers”), which preferably react during the emulsion polymerization tocrosslink the otherwise separate copolymer chains and/or to function asgrowth sites for adjacent copolymer chains. Examples of suitablecompounds for the multi-unsaturated monomers include monomers having twoor more ethylenically-unsaturated groups, such as multi-functional(meth)acrylate monomers, multi-functional vinyl monomers,multi-functional maleate monomers, multi-functional olefin monomers, andthe like. Illustrative multi-unsaturated monomers include thoserepresented by the following structure:

where groups R₆ and R₇ may independently be a hydrogen atom or anorganic group, such as a C₁-C₆ alkyl group, and more preferably ahydrogen atom or a methyl group. Additionally, one or both of thehydrogen atoms attached to the terminal carbon atom of eachethylenically-unsaturated group may independently be replaced with agroup R₆. Groups X may each independently be a —COO— ester group, may beindependently be substituted with an organic group, such as ahydrocarbon group (e.g., for producing an allyl terminal group) oranother heteroatom-containing group (e.g., another type of divalentstep-growth linkage group), or may be omitted.

Group R₈ may be any suitable divalent group, such as, for example, a C₂,C₃, C₄, C₅, or C₆ hydrocarbon group, where one or more hydrogen atoms ofthe hydrocarbon group may each optionally be substituted with a groupR₆, a polar group (e.g., a hydroxy group, an amino group, and the like),and an alkoxy group, for example. In some embodiments, group R₈ isselected from a C₂, C₃, C₄, C₅, or C₆ hydrocarbon moiety. In someembodiments, group R₈ may include one or more cyclic groups, which maybe saturated, unsaturated, or aromatic, and may be monocyclic orpolycyclic groups.

In additional preferred embodiments, each unsaturated bond (e.g., doublebond) is connected to a terminal carbon of the molecule (e.g., a CH₂group), as shown in Formula 4. In further additional embodiments, one ormore hydrogen atoms of the hydrocarbon group in group R₈ may also besubstituted with a branched ethylenically-unsaturated group, such thatthe multi-unsaturated monomer may have a total of three or moreethylenically-unsaturated groups.

Specific examples of suitable multi-functional (meth)acrylates includepolyhydric alcohol esters of acrylic acid or methacrylic acid, such asethanediol di(meth)acrylate, propanediol di(meth)acrylate, butanedioldi(meth)acrylate (e.g., 1,3-butanediol dimethacrylate and 1,4-butanedioldi(meth)acrylate), heptanediol di(meth)acrylate, hexanedioldi(meth)acrylate, trimethylolethane tri(meth)acrylate trimethylolpropanetri(meth)acrylate, trimethylolbutane tri(meth)acrylate,trimethylolheptane tri(meth)acrylate, trimethylolhexanetri(meth)acrylate, tetramethylol methane tetra(meth)acrylate,dipropylene glycol di(meth)acrylate, trimethylol hexanetri(meth)acrylate, pentaerythritol tetra(meth)acrylate, isosorbidedi(meth)acrylate, and mixtures thereof.

In some embodiments, group R₆, R₇, and/or R₈, may form one or more ringstructures with one or more of the terminal carbon atoms of theethylenically-unsaturated groups. These can formethylenically-unsaturated ring structures, such as norbornenemethylolacrylate, dicyclopentadiene, mixtures thereof, and the like.

In alternative embodiments, other linkage monomers can be used insteadof (or in addition to) the multi-functional (meth)acrylates, where thelinkage monomers include at least two different functional groups, suchas an ethylenically-unsaturated group and an oxirane group (e.g., GMA orglycidyl acrylate). In these embodiments, one of theethylenically-unsaturated groups in Formula 5 shown above may bereplaced with an alternative functional group that is configured toreact with a reciprocating functional group of a copolymer chain (e.g.,an oxirane group for reacting with a hydroxyl group of a copolymerchain).

However, in some preferred embodiments, the reactant components aresubstantially free or completely free of glycidyl methacrylate (“GMA”)and glycidyl acrylate. In more preferred embodiments, the reactantcomponents are substantially free or completely free of monomers havingoxirane groups. These preferred embodiments may also apply to resultinglatex copolymer, the latex emulsion, the coating composition, and thecured coating. As such, in preferred embodiments, the latex copolymer,the latex emulsion, the coating composition, and the cured coating areeach also substantially free or completely free of mobile or bound GMAand glycidyl acrylate, and/or monomers having oxirane groups. In theseembodiments, the monomer shown above in Formula 5 preferably includestwo or more ethylenically-unsaturated groups.

The multi-unsaturated (and/or other linkage) monomers, if used,preferably constitute greater than about 1%, more preferably greaterthan about 5%, more preferably greater than about 8%, even morepreferably greater than about 9%, and in some embodiments, greater thanabout 10%, based on the total weight of the reactant monomers. Themulti-unsaturated monomers may also constitute less than about 25%, morepreferably less than about 20%, and even more preferably less than about15%, based on the total weight of the reactant monomers.

Examples of suitable ethylenically-unsaturated acid-functional monomersinclude ethylenically-unsaturated carboxylic acid monomers, anhydridesthereof, salts thereof, and mixtures thereof. Illustrativeethylenically-unsaturated carboxylic acid monomers include thoserepresented by the following structure:

where the group R₉ may be a hydrogen atom or an organic group, such as aC₁-C₆ alkyl group, and more preferably a hydrogen atom or a methylgroup. Additionally, one or both of the hydrogen atoms attached to theterminal carbon atom of the ethylenically-unsaturated group may bereplaced with an independant group R₉. Group R₁₀ may be any suitabledivalent group, such as, for example, a C₁-C₁₆ alkyl or alkenyl group,which can be substituted with one or more (e.g., 1-3) groups such ashydroxy group, halogen groups, phenyl groups, oxirane groups, and alkoxygroups, for example.

In preferred embodiments, the ethylenically-unsaturated acid-functionalmonomers are free of oxirane groups or halogen groups, and morepreferably both. The integer “n” may be zero or one, more preferablyzero such that group R₁₀ is omitted and the carboxyl (—COOH) groupextends directly from the unsaturated group. In preferred embodiments,the unsaturated bond (e.g., double bond) is connected to a terminalcarbon of the molecule (e.g., a CH₂ group), as shown in Formula 5.

Examples of suitable ethylenically-unsaturated carboxylic acid monomersinclude acrylic acid, methacrylic acid, alpha-chloroacrylic acid,alpha-cyanoacrylic acid, crotonic acid, alpha-phenylacrylic acid,beta-acryloxypropionic acid, fumaric acid, maleic acid, sorbic acid,alpha-chlorosorbic acid, angelic acid, cinnamic acid, p-chlorocinnamicacid, beta-stearylacrylic acid, citraconic acid, mesaconic acid,glutaconic acid, aconitic acid, tricarboxyethylene, 2-methyl maleicacid, itaconic acid, 2-methyl itaconic acid, methyleneglutaric acid, andthe like, and mixtures thereof. Preferred ethylenically-unsaturatedcarboxylic acid monomers include acrylic acid, methacrylic acid,crotonic acid, fumaric acid, maleic acid, 2-methyl maleic acid, itaconicacid, 2-methyl itaconic acid, and mixtures thereof.

Examples of suitable ethylenically-unsaturated anhydride monomersinclude compounds derived from the above-discussedethylenically-unsaturated carboxylic acid monomers (e.g., as pureanhydride or mixtures of such). Preferred ethylenically-unsaturatedanhydrides include acrylic anhydride, methacrylic anhydride, and maleicanhydride. If desired, salts of the above ethylenically-unsaturatedcarboxylic acid monomers may also be employed.

The ethylenically-unsaturated acid-functional monomers may collectivelyconstitute greater than about 1%, more preferably greater than about 3%,and even more preferably greater than about 5% by weight, based on thetotal weight of the reactant monomers. The ethylenically-unsaturatedacid-functional monomers may also collectively constitute less thanabout 40%, more preferably less than about 30%, and even more preferablyless than about 20%, based on the total weight of the reactant monomers.

The optional polymerizable surfactants may assist in dispersing thereactant monomers in the aqueous carrier, as well as optionallypolymerizing with each other and/or the reactant monomers to form thecopolymer chains. As such, in some embodiments, the polymerizablesurfactants are preferably capable of polymerizing or otherwise reactingunder free radical-initiated polymerization conditions. For instance,the polymerizable surfactants may each have one or more hydrophobicportions, one or more hydrophilic portions, and anethylenically-unsaturated group located at the hydrophobic portion, atthe hydrophilic portion, or in-between.

The hydrophobic portion(s) may be any suitable substituted orunsubstituted hydrocarbon chain, such as a substituted or unsubstitutedalkyl or alkenyl group, a substituted or unsubstituted cyclichydrocarbon group, a substituted or unsubstituted aromatic hydrocarbongroup, and combinations thereof. The hydrophobic portion(s) preferablyinclude one or more non-polar groups, such as one or more aromaticgroups.

The hydrophilic portion(s) may be any suitable substituted orunsubstituted hydrocarbon chain, such as a substituted or unsubstitutedalkyl or alkenyl chain, optionally with one or more ether linkages,which terminates in a polar group. The polar group may include one ormore hydroxyl groups, acid groups (e.g., carboxylic acid groups),sulfonate groups, sulfinate groups, sulfate groups, phosphate groups,phosphinate groups, phosphonate groups, salt derivatives thereof, andcombinations thereof.

Examples of suitable polymerizable surfactants include those disclosedin U.S. Publication No. 2002/0155235; and those commercially availableunder the tradename “REASOAP” from Adeka Corporation, Tokyo, Japan.,under the tradenames “NOIGEN” and “HITENOL” from Da-Ichi Kogyo SiyyakuCo., Ltd., Tokyo, Japan; and under the tradename “SIPOMER” from SolvayRhodia, Brussels, Belgium.

In embodiments that include polymerizable surfactants, the polymerizablesurfactants may constitute greater than about 1%, more preferablygreater than about 2%, and even more preferably greater than about 3% byweight, based on the total weight of the reactant monomers. Thepolymerizable surfactant may also constitute less than about 25%, morepreferably less than about 15%, and even more preferably less than about10% by weight, based on the total weight of the reactant monomers.

In preferred embodiments, the reactant monomers include a combination ofone or more styrene-offset monomers, one or more non-cyclic(meth)acrylate monomers, and one or more ethylenically-unsaturatedacid-functional monomers. In certain preferred embodiments, the reactantmonomer further include one or both of: (i) one or moremulti-unsaturated monomers, and (ii) one or more polymerizablesurfactants.

The non-cyclic (meth)acrylates may constitute from about 20% to about50% by weight, and more preferably from about 30% to about 40% byweight; the (meth)acrylic acids may constitute from about 1% to about25% by weight, and more preferably from about 5% to about 15% by weight;and the optional polymerizable surfactants may constitute from 0% toabout 15% by weight, and more preferably from about 5% to about 10% byweight; based on the entire weight of the reactant monomers used toproduce the latex copolymer.

In some aspects, some of the non-cyclic (meth)acrylate monomers mayterminate in polar groups, such as hydroxyl groups. In theseembodiments, the non-cyclic (meth)acrylate monomers with the terminalpolar groups (preferably hydroxyl groups) may constitute from about 1%to about 20% by weight, and more preferably from about 5% to about 15%by weight; based on the entire weight of the reactant monomers. Thenon-cyclic (meth)acrylate monomers without the terminal polar groups mayaccordingly constitute the remainder of the non-cyclic (meth)acrylatemonomers.

A first more preferred combination of reactant monomers includes one ormore ethylenically-unsaturated polycyclic monomers, one or morenon-aromatic (meth)acrylate monomers, one or more (meth)acrylic acids,and optionally one or both of: (i) one or more multi-functional(meth)acrylate monomers and (ii) one or more polymerizable surfactants.

In this embodiment, the ethylenically-unsaturated polycyclic monomer(s)preferably constitute at least about 10% by weight of the monomers usedto produce the latex copolymer, and the reactant monomers may alsooptionally include one or more non-styrenic, ethylenically-unsaturatedmonocyclic monomers. In some embodiments, the ethylenically-unsaturatedpolycyclic monomer(s) preferably constitute at least about 20% byweight, and/or at least about 30% by weight, based on a total weight ofthe monomers used to produce the latex copolymer.

A second more preferred combination of reactant monomers includes one ormore ethylenically-unsaturated monocyclic monomers each having a ringstructure with 3-5 atoms in the ring, one or more non-cyclic(meth)acrylate monomers, one or more (meth)acrylic acids, and optionallyone or both of: (i) one or more multi-functional (meth)acrylate monomersand (ii) one or more polymerizable surfactants.

In this embodiment, the ethylenically-unsaturated, monocyclic monomer(s)with 3-5 atom rings preferably constitute at least about 5% by weight orat least about 10% by weight of the monomers used to produce the latexcopolymer, and the reactant monomers may also optionally include one ormore non-styrenic, ethylenically-unsaturated monocyclic monomers havingsix or more atoms in the ring. In some embodiments, theethylenically-unsaturated monocyclic monomers each having a ringstructure with 3-5 atoms in the ring preferably constitute at leastabout 20% by weight, and/or at least about 30% by weight, based on atotal weight of the monomers used to produce the latex copolymer.

A third more preferred combination of reactant monomers includes one ormore ethylenically-unsaturated polycyclic monomers, one or moreethylenically-unsaturated monocyclic monomers each having a ringstructure with 3-5 atoms in the ring, one or more non-cyclic(meth)acrylate monomers, one or more (meth)acrylic acids, and optionallyone or both of: (i) one or more multi-functional (meth)acrylate monomersand (ii) one or more polymerizable surfactants.

In this embodiment, the combined concentrations of theethylenically-unsaturated polycyclic monomer(s) and theethylenically-unsaturated monocyclic monomer(s) each having a ringstructure with 3-5 atoms in the ring preferably constitute at leastabout 10% by weight of the monomers used to produce the latex copolymer.In this case, the reactant monomers may also optionally include one ormore non-styrenic, ethylenically-unsaturated monocyclic monomers havingsix or more atoms in the ring. In some embodiments, the combinedconcentrations of the ethylenically-unsaturated polycyclic monomer(s)and the ethylenically-unsaturated monocyclic monomer(s) each having aring structure with 3-5 atoms in the ring preferably constitute at leastabout 10% by weight, at least about 20% by weight, or at least about 30%by weight, based on a total weight of the monomers used to produce thelatex copolymer.

The aqueous carrier may include water, and optionally, one or moreorganic solvents. Examples of suitable organic solvents for use in theaqueous carrier may include methanol, ethanol, isopropyl alcohol, butylalcohols (e.g., n-butanol and buytl glycol), 2-butoxyethanol,2-(2-butoxyethoxy)ethanol (i.e., butyl carbitol), aromatic solvents,isophorones, glycol ethers, glycol ether acetates, acetone, methyl-ethylketones (MEK), N,N-dimethylformamides, ethylene carbonates, propylenecarbonates, diglymes, N-methylpyrrolidones (NMP), ethyl acetates,ethylene diacetates, propylene glycol diacetates, alkyl ethers ofethylene, propylene glycol monoacetates, toluene, xylenes, andcombinations thereof.

Optionally, one or more non-polymerizable surfactants (e.g.,non-polymeric surfactants) may also be used (i.e., alone or incombination with one or more polymerizable surfactants, or one or morepolymeric surfactant such as, e.g., acrylic polymers havingwater-dispersing groups such as neutralized acid or base groups), suchas surfactants that can support emulsion polymerization reactions. Forexample, the non-polymerizable surfactant(s) may include surfactantscontaining sulfonate groups, sulfate groups, phosphate groups,phosphinate groups, phosphonate groups, and combinations thereof; aswell as ethoxylated surfactants. An example of a non-polymerizablesurfactant includes dodecylbenzene sulfonic acid and sulfonates thereof(e.g., dodecylbenzene sulfonate salts, and particularly amine- orammonia-neutralized salts).

The concentration of non-polymerizable surfactants may vary depending onthe types and concentrations of the reactant components, including thepresence of any polymerizable surfactants. In embodiments that includenon-polymerizable surfactants, the non-polymerizable surfactants mayconstitute greater than about 0.01%, greater than about 0.05%, orgreater than about 0.1% by weight, relative to a total weight of thereactant components. The non-polymerizable surfactants may alsoconstitute less than about 10%, less than about 7%, or less than about5% by weight, relative to the total weight of the reactant components.

Although it is contemplated that surfactants that are non-polymerizableand non-polymeric can be used in some embodiments, it is generallypreferable to use a polymeric surfactant and/or a polymerizablesurfactant to, for example, minimize or eliminate the possibility ofsurfactant migrating out of the cured coating and into the packagedproduct.

In some preferred embodiments, a polymeric surfactant having asufficient amount of water-dispersing groups (e.g., salt, orsalt-forming groups, such as neutralized acid or neutralized basegroups) to facilitate the emulsion polymerization of the reactantmonomers may be used to support the emulsion polymerization, eitheralone or in combination with any of the other types of surfactantsreferenced herein. Examples of polymer-based surfactants include thosedisclosed in U.S. Pat. No. 8,092,876 and PCT International PublicationNumber WO2014/140057, each of which is incorporated by reference to theextent that it doesn't conflict with the present disclosure. In theseembodiments, the polymer surfactants can constitute up to about 40% bysolids weight in the aqueous dispersion. Such polymeric surfactants maybe acrylic polymers, epoxy polymers, polyester polymers, polyolefins(e.g., (poly)ethylene (meth)crylic acid copolymers such as, e.g., thePRIMACOR 5980i or PRIMACOR 5990i products), polyurethane polymers, orcopolymers or mixtures thereof, with acrylic polymeric surfactants beingparticularly preferred.

The emulsion polymerization process may be conducted in a variety ofmanners. In some preferred embodiments, the emulsion polymerizationprocess uses a pre-emulsion monomer mixture in which some or all of thereactant components and any optional surfactants are dispersed in theaqueous carrier under agitation to form a stable pre-emulsion.

A portion of the surfactants (e.g., polymerizable and/ornon-polymerizable) and a portion of the aqueous carrier may also beintroduced into a reactor, and are preferably heated, agitated, and heldunder nitrogen sparge to assist in the subsequent polymerizationreactions. Preferred temperatures for heating the surfactant dispersioninclude temperatures greater than about 65° C., and more preferably fromabout 70° C. to about 90° C.

The pre-emulsion may then be fed to the heated aqueous dispersion in thereactor incrementally or continuously over time. Alternatively, incertain embodiments a batch or semi-batch process may be used topolymerize the reactant monomers in the aqueous dispersion, as describedin, for example, U.S. Pat. No. 8,092,876. In further embodiments, thepolymerization process can occur in a classic two-stage (or multiplestage) core-shell arrangement. Alternatively, the polymerization processcan occur in a multiple stage “inverse core shell” arrangement asdiscussed in International Publication No. WO2015/002961. Intermediatehybrids of these processes may also be used.

One or more polymerization initiators may also be added to the aqueousdispersion (e.g., along with the reactant components) at any suitabletime(s) to initiate the emulsion polymerization. Suitable polymerizationinitiators include free-radical initiators, such as one or moreperoxides and/or persulfates and similar compounds. Examples of suitableperoxides include hydroperoxides such as t-butyl hydroperoxide, hydrogenperoxide, t-amyl hydroperoxide, methyl hydroperoxide, and cumenehydroperoxide; peroxides such as benzoyl peroxide, caprylyl peroxide,di-t-butyl peroxide, ethyl 3,3′-di(t-butylperoxy) butyrate, ethyl3,3′-di(t-amylperoxy) butyrate, t-amylperoxy-2-ethyl hexanoate, andt-butylperoxy pivilate; peresters such as t-butyl peracetate, t-butylperphthalate, and t-butyl perbenzoate; as well as percarbonates; andmixtures thereof.

Azoic compounds can also be used to generate free radicals such as2,2′-azo-bis(isobutyronitrile), 2,2′-azo-bis(2,4-dimethylvaleronitrile),and 1-t-butyl-azocyanocyclohexane, and mixtures thereof. Examples ofsuitable persulfates include persulfates of ammonium or alkali metal(potassium, sodium or lithium). Perphosphates can be also a source offree radicals, and mixtures thereof.

Polymerization initiators can be used alone or as the oxidizingcomponent of a redox system, which also typically includes a reducingcomponent such as ascorbic acid, malic acid, glycolic acid, oxalic acid,lactic acid, thiogycolic acid, or an alkali metal sulfite, morespecifically a hydrosulfite, hyposulfite or metabisulfite, such assodium hydrosulfite, potassium hyposulfite and potassium metabisulfite,or sodium formaldehyde sulfoxylate, ferrous complexes (e.g., ferroussulphate heptahydrate), and mixtures thereof. The reducing component isfrequently referred to as an accelerator or a catalyst activator.

The initiator and accelerator (if used) are preferably each used inconcentrations greater than about 0.001%, more preferably greater thanabout 0.01%, and more preferably greater than about 0.1% by weight,relative to the total weight of the reactant components. The initiatorand accelerator (if used) are also each preferably used inconcentrations less than about 5%, more preferably less than about 3%,and in some embodiments, less than about 1% by weight, relative to thetotal weight of the reactant components.

Promoters such as chloride and sulfate salts of cobalt, iron, nickel orcopper can be used in small amounts, if desired. Examples of redoxcatalyst systems include tert-butyl hydroperoxide/sodium formaldehydesulfoxylate/Fe(II), and ammonium persulfate/sodium bisulfite/sodiumhydrosulfite/Fe(II).

The emulsion polymerization may continue for a suitable duration topolymerize the reactant components with a free-radical initiatedpolymerization process. This can produce each latex copolymer as aparticle dispersed or otherwise suspended in the aqueous solution. And,in some embodiments, where each latex copolymer has linear and/orbranched copolymer chains that are preferably cross-linked with linkagesderived from the multi-unsaturated or other linkage monomers.

After the polymerization is completed, in some embodiments, at least aportion of the carboxylic acid groups and/or anhydride groups of thelatex copolymer (or other salt-forming groups such as, e.g.,neutralizable base groups) may be neutralized or partially neutralizedwith a suitable basic compound (or other suitable neutralizing compound)to produce water-dispersing groups. The basic compound used forneutralization is preferably a fugitive base, more preferably a fugitivenitrogen base (e.g., ammonia and primary, secondary, and/or tertiaryamines), with amines being particularly preferred. Other suitable basesmay include the metallic bases described in the application filed on thesame date herewith and entitled “Latex Polymers Made UsingMetallic-Base-Neutralized Surfactant and Blush-Resistant CoatingCompositions Containing Such Polymers” 62/387,129.

Some examples of suitable amines are trimethyl amine, dimethylethanolamine (also known as dimethylamino ethanol), methyldiethanol amine,triethanol amine, ethyl methyl ethanol amine, dimethyl ethyl amine,dimethyl propyl amine, dimethyl 3-hydroxy-1-propyl amine, dimethylbenzylamine, dimethyl 2-hydroxy-1-propyl amine, diethyl methyl amine, dimethyl1-hydroxy-2-propyl amine, triethyl amine, tributyl amine, N-methylmorpholine, and mixtures thereof. Triethyl amine and dimethyl ethanolamine are preferred amines.

The degree of neutralization required may vary considerably dependingupon the amount of acid or base groups included in the latex copolymer,and the degree of dispersibility that is desired. In embodiments inwhich neutralized acid groups are used for water dispersibility,preferred acid numbers for the copolymer prior to neutralization includeacid numbers greater than about 40, more preferably greater than about80, and even more preferably greater than about 100 milligrams (mg)potassium hydroxide (KOH) per gram of the latex copolymer.

Preferred acid numbers for the latex copolymer prior to neutralizationalso include acid numbers less than about 400, more preferably less thanabout 350, and even more preferably less than about 300 mg KOH per gramof the latex copolymer. Acid numbers referred to herein may becalculated pursuant to BS EN ISO 3682-1998 standard, or alternativelymay be theoretically determined based on the reactant monomers.

Typically, to render the latex copolymer water-dispersible, at least 25%of the acid groups of the latex copolymer are neutralized, preferably atleast 30% are neutralized, and more preferably at least 35% areneutralized. Preferably, the latex copolymer includes a sufficientnumber of water-dispersing groups to form a stable dispersion in theaqueous carrier. Furthermore, in embodiments incorporating polymerizablesurfactants and/or other surfactants, the hydrophilic portions of thesurfactant may also assist in dispersing the latex copolymer in theaqueous carrier.

While the latex copolymer has been primarily described herein withacid-based water-dispersing groups that are neutralized with basiccompounds, in alternative embodiments, the water-dispersing groups maybe basic groups that are neutralized with acidic compounds. Examples ofsuitable basic groups for this embodiment include those disclosed inO'Brien et al., U.S. Pat. No. 8,092,876. Examples of suitable acidicneutralizing compounds include formic acid, acetic acid, hydrochloricacid, sulfuric acid, and mixtures thereof.

After polymerization and/or neutralization, the resulting particles ofthe latex copolymer are provided in the aqueous carrier as a dispersionof the latex copolymer. In some preferred embodiments, the copolymerchains of the latex copolymer may include one or more ester groups, oneor more hydroxyl groups, one or more water-dispersing groups (e.g.,carboxylic acid groups, anhydride groups, and/or neutralized saltsthereof), and/or one or more cyclic groups (e.g., aromatic groups).Additionally, the copolymer chains may be cross-linked by one or morelinkages from the multi-unsaturated monomers to produce the latexcopolymer.

The coating composition may be formulated from the latex emulsion,optionally with the inclusion of one or more additives and/or byrheological modification for different coating applications (e.g.,diluted for spray coating applications). In embodiments in which thecoating composition includes one or more additives, the additivespreferably do not adversely affect the latex emulsion, or a curedcoating formed from the coating composition. For example, such optionaladditives may be included in the coating composition to enhancecomposition aesthetics, to facilitate manufacturing, processing,handling, and application of the composition, and to further improve aparticular functional property of the coating composition or a curedcoating resulting therefrom.

Such optional additives include, for example, catalysts, dyes, pigments,toners, extenders, fillers, lubricants, anticorrosion agents, flowcontrol agents, thixotropic agents, dispersing agents, antioxidants,adhesion promoters, light stabilizers, co-resins and mixtures thereof.Each optional additives is preferably included in a sufficient amount toserve its intended purpose, but not in such an amount to adverselyaffect the coating composition or a cured coating resulting therefrom.

One preferred optional additive is a catalyst to increase the rate ofcure. Examples of catalysts, include, but are not limited to, strongacids (e.g., dodecylbenzene sulphonic acid (DDBSA, available as CYCAT600 from Cytec), methane sulfonic acid (MSA), p-toluene sulfonic acid(pTSA), dinonylnaphthalene disulfonic acid (DNNDSA), and triflic acid),quaternary ammonium compounds, phosphorous compounds, and tin, titanium,and zinc compounds. Specific examples include, but are not limited to, atetraalkyl ammonium halide, a tetraalkyl or tetraaryl phosphonium iodideor acetate, tin octoate, zinc octoate, triphenylphosphine, and similarcatalysts known to persons skilled in the art.

If used, the catalyst is preferably present in an amount of at leastabout 0.01% by weight, and more preferably at least about 0.1% byweight, based on the total solids weight of the coating composition.Furthermore, if used, the catalyst is also preferably present in annon-volatile amount of no greater than about 3% by weight, and morepreferably no greater than about 1% by weight, based on the total solidsweight of the coating composition.

Another useful optional ingredient is a lubricant (e.g., a wax), whichfacilitates manufacture of metal closures and other fabricated coatedarticles by imparting lubricity to sheets of coated metal substrate.Preferred lubricants include, for example, Carnauba wax andpolyethylene-type lubricants. If used, a lubricant is preferably presentin the coating composition in an amount of at least about 0.1% byweight, and preferably no greater than about 2% by weight, and morepreferably no greater than about 1% by weight, based on the total solidsweight of the coating composition.

Another useful optional ingredient is an organosilicon material, such asa siloxane-based and/or polysilicone-based materials. Representativeexamples of suitable such materials are disclosed in InternationalPublication Nos. WO/2014/089410 and WO/2014/186285.

Another useful optional ingredient is a pigment, such as titaniumdioxide. If used, a pigment is present in the coating composition in anamount of no greater than about 70% by weight, more preferably nogreater than about 50% by weight, and even more preferably no greaterthan about 40% by weight, based on the total solids weight of thecoating composition.

The coating composition may also incorporate one or more optional curingagents (e.g., crosslinking resins, sometimes referred to as“crosslinkers”). The choice of particular crosslinker typically dependson the particular product being formulated. For example, some coatingsare highly colored (e.g., gold-colored coatings). These coatings maytypically be formulated using crosslinkers that themselves tend to havea yellowish color. In contrast, white coatings are generally formulatedusing non-yellowing crosslinkers, or only a small amount of a yellowingcrosslinker. Preferred curing agents are substantially free of BPA, BPF,BPS, glycidyl ether compounds thereof (e.g., BADGE), and epoxy novolacs.

Any of the well known hydroxyl-reactive curing resins can be used. Forexample, phenoplast, blocked isocyanates, and aminoplast curing agentsmay be used, as well as combinations thereof. Phenoplast resins includethe condensation products of aldehydes with phenols. Formaldehyde andacetaldehyde are preferred aldehydes. Various phenols can be employedsuch as phenol, cresol, p-phenylphenol, p-tert-butylphenol,p-tert-amylphenol, and cyclopentylphenol.

Aminoplast resins are the condensation products of aldehydes such asformaldehyde, acetaldehyde, crotonaldehyde, and benzaldehyde with aminoor amido group-containing substances such as urea, melamine, andbenzoguanamine. Examples of suitable aminoplast crosslinking resinsinclude benzoguanamine-formaldehyde resins, melamine-formaldehyderesins, esterified melamine-formaldehyde, and urea-formaldehyde resins.One specific example of a suitable aminoplast crosslinker is the fullyalkylated melamine-formaldehyde resin commercially available from CytecIndustries, Inc. under the trade name of CYMEL 303.

As examples of other generally suitable curing agents are the blocked ornon-blocked aliphatic, cycloaliphatic or aromatic di-, tri-, orpoly-valent isocyanates, such as hexamethylene diisocyanate (HMDI),cyclohexyl-1,4-diisocyanate, and the like. Further examples of generallysuitable blocked isocyanates include isomers of isophorone diisocyanate,dicyclohexylmethane diisocyanate, toluene diisocyanate, diphenylmethanediisocyanate, phenylene diisocyanate, tetramethyl xylene diisocyanate,xylylene diisocyanate, and mixtures thereof. In some embodiments,blocked isocyanates are used that have a number-average molecular weightof at least about 300, more preferably at least about 650, and even morepreferably at least about 1,000.

The concentration of the curing agent (e.g., crosslinker) in the coatingcomposition may depend on the type of curing agent, the time andtemperature of the bake, and the molecular weights of the copolymerparticles. If used, the crosslinker is typically present in an amount ofup to about 50% by weight, preferably up to about 30% by weight, andmore preferably up to about 15% by weight. If used, the crosslinker istypically present in an amount of at least about 0.1% by weight, morepreferably at least about 1% by weight, and even more preferably atleast about 1.5% by weight. These weight percentages are based on thetotal resin solids weight of the coating composition.

In some embodiments, the coating composition may be cured without theuse of an external crosslinker (e.g., without phenolic crosslinkers).Additionally, the coating composition may be substantially free offormaldehyde and formaldehyde-conditioning materials, more preferablyessentially free of these compounds, even more preferably essentiallycompletely free of these compounds, and most preferably completely freeof these compounds.

In preferred embodiments, the coating composition is also substantiallyfree or completely free of any structural units derived from bisphenol A(“BPA”), bisphenol F (“BPF”), bisphenol S (“BPS”), or any diepoxidesthereof (e.g., diglycidyl ethers thereof such as the diglycidyl ether ofBPA (“BADGE”)). In addition, the coating composition is preferablysubstantially free or completely free of any structural units derivedfrom a dihydric phenol, or other polyhydric phenol, having estrogenicagonist activity great than or equal to that of4,4′-(propane-2,2-diyl)diphenol. More preferably, the coatingcomposition is substantially free or completely free of any structuralunits derived from a dihydric phenol, or other polyhydric phenol, havingestrogenic agonist activity greater than or equal to that of BPS. Insome embodiments, the coating composition is substantially free orcompletely free of any structural units derived from a bisphenol.

Even more preferably, the coating composition is substantially free orcompletely free of any structural units derived from a dihydric phenol,or other polyhydric phenol, having estrogenic agonist activity greaterthan 4,4′-(propane-2,2-diyl)bis(2,6-dibromophenol). Optimally, thecoating composition is substantially free or completely free of anystructural units derived from a dihydric phenol, or other polyhydricphenol, having estrogenic agonist activity greater than2,2-bis(4-hydroxyphenyl)propanoic acid. The same is preferably true forany other components of a composition including the coating composition.See, for example, U.S. Publication No. 2013/0316109 for a discussion ofsuch structural units and applicable test methods.

In some further embodiments, the coating composition is substantiallyfree or completely free of any acrylamide-type monomers (e.g.,acrylamides or methacrylamide). Moreover, in some embodiments, thecoating composition is substantially free or completely free of one ormore of styrene (whether free or polymerized) and/or substituted styrenecompounds (whether free or polymerized). As discussed above, in theseembodiments, the reactant monomers may include otherethylenically-unsaturated aromatic compounds and/orethylenically-unsaturated alicyclic compounds, such as aromatic(meth)acrylates and/or alicyclic (meth)acrylates, for example. Inadditional further embodiments, the coating composition is substantiallyfree or completely free of halogenated monomers (whether free orpolymerized), such as chlorinated vinyl monomers.

The coating composition may also optionally be rheologically modifiedfor different coating applications. For example, the coating compositionmay be diluted with additional amounts of the aqueous carrier to reducethe total solids content in the coating composition. Alternatively,portions of the aqueous carrier may be removed (e.g., evaporated) toincrease the total solids content in the coating composition. The finaltotal solids content in the coating composition may vary depending onthe particular coating application used (e.g., spray coating), theparticular coating use (e.g., for interior can surfaces), the coatingthickness, and the like.

In some embodiments, the coating composition preferably has a totalsolids weight greater than about 5%, more preferably greater than about10%, and even more preferably greater than about 15%, based on the totalweight of the coating composition. The coating composition alsopreferably has a total solids weight less than about 80%, morepreferably less than about 60%, and even more preferably less than about50%, based on the total weight of the coating composition. The aqueouscarrier may constitute the remainder of the weight of the coatingcomposition.

In some embodiments, such as for certain spray coating applications(e.g., inside spray for food or beverage cans including, e.g., aluminumbeverage cans), the coating composition may have a total solids weightgreater than about 5%, more preferably greater than about 10%, and evenmore preferably greater than about 15%, based on the total weight of thecoating composition. In these embodiments, the coating composition mayalso have a total solids weight less than about 40%, more preferablyless than about 30%, and even more preferably less than about 25%, basedon the total weight of the coating composition. In some of theseembodiments, the coating composition may have a total solids weightranging from about 18% to about 22%. The aqueous carrier may constitutethe remainder of the weight of the coating composition.

The coating composition preferably includes at least a film-formingamount of the latex copolymer. In some embodiments, the latex copolymerpreferably constitutes greater than about 50%, more preferably greaterthan about 65%, and even more preferably greater than about 80% byweight of the coating composition, based on the entire weight of thetotal resin solids in the coating composition. The particles of thelatex copolymer may constitute 100% or less, more typically less thanabout 99%, and even more typically less than about 95% by weight of thecoating composition, based on the entire weight of the total resinsolids in the coating composition.

If desired, the coating composition may also include one or more otheroptional polymers in addition to the latex copolymers, such as, forexample, one or more acrylic polymers, alkyd polymers, epoxy polymers,polyolefin polymers, polyurethane polymers, polysilicone polymers,polyester polymers, and copolymers and mixtures thereof.

As previously discussed, the aqueous carrier of the coating compositionpreferably includes water and may further include one or more optionalorganic solvents. In some embodiments, water constitutes greater thanabout 20% by weight, more preferably greater than about 35% by weight,and even more preferably greater than about 50% by weight of the totalweight of the aqueous carrier. In some embodiments, water constitutes100% or less, more preferably less than about 95% by weight, and evenmore preferably less than about 90% by weight of the total weight of theaqueous carrier.

While not intending to be bound by theory, the inclusion of a suitableamount of an organic solvent can be advantageous, in some embodiments(e.g., for certain coil coating applications to modify flow and levelingof the coating composition, control blistering, and maximize the linespeed of the coil coater). Accordingly, in certain embodiments, theorganic solvents may constitute greater than 0%, more preferably greaterthan about 5%, and even more preferably greater than about 10% by weightof the aqueous carrier, based on the total weight of the aqueouscarrier. In these embodiments, the organic solvents may also constituteless than about 80%, more preferably less than about 50%, and even morepreferably less than about 40% by weight of the aqueous carrier, basedon the total weight of the aqueous carrier.

The coating composition preferably has a viscosity suitable for a givencoating application. In some embodiments, such as for certain spraycoating applications (e.g., those discussed below for FIGS. 2 and 3),the coating composition may have an average viscosity greater than about5 seconds, more preferably greater than 10 seconds, and even morepreferably greater than about 15 seconds, based on the Viscosity Testdescribed below (Ford Viscosity Cup #4 at 25° C.). In some embodiments,the coating composition may also have an average viscosity less thanabout 40 seconds, more preferably less than 30 seconds, and even morepreferably less than about 25, based on the Viscosity Test describedbelow.

The coating composition of the present disclosure with the aqueousdispersion of the latex copolymer particles may be applied ona varietyof different substrates using a variety of different coating techniques.In preferred embodiments, the coating composition is applied as aninside spray coating. As briefly described above, cured coatings formedfrom the coating composition are particularly suitable for use on metalfood and beverage cans (e.g., two-piece cans, three-piece cans, and thelike). Two-piece cans (e.g., two-piece beer or soda cans and certainfood cans) are typically manufactured by a drawn and ironing (“D&I”)process. The cured coatings are also suitable for use in food orbeverage contact situations (collectively referred to herein as“food-contact”), and may be used on the inside or outside of such cans.

For instance, FIG. 1 shows container 20, which is a simplified exampleof a food or beverage container that may be coated with the coatingcomposition of the present disclosure. Container 20 may be a two-piececan having body 22 and lid piece 24, where body 22 includes sidewall 26and bottom end 28. Lid piece 24 may be sealed to body 22 in any suitablemanner, and may optionally include one or more tabs (not shown) tofacilitate peeling off or opening of lid piece 24 or a portion thereof(e.g., as is common for beverage can ends and easy-open food can ends).

Sidewall 26 and bottom end 28 respectively include interior surfaces 30and 32, and suitable substrate materials for sidewall 26 and bottom end28 include metallic materials, such as aluminum, iron, tin, steel,copper, and the like. One or more portions of interior surfaces 30 and32 (or exterior surface) may be coated with coating 34, which is a curedcoating formed from the coating composition of the present disclosure.In some embodiments, the interior surface of lid piece 24 may also becoated with coating 34.

A suitable spray coating technique for applying the coating compositionto an interior surface of a food or beverage can (e.g., surfaces 30 and32) may involve spraying the coating composition using one or more spraynozzles capable of uniformly coating the inside of the can. For example,FIG. 2 illustrates a side view, and FIG. 3 illustrates a top view of anexample setup for spray coating the coating composition onto theinterior surfaces 30 and 32 of a can 20 with a spray nozzle 36 (prior tonecking of an upper portion of sidewall 26). As shown, the spray nozzle36 is preferably a controlled-pattern nozzle capable of generating adesired spray pattern, such as spray 38 having a flat-fan pattern asgenerally illustrated in FIGS. 2 and 3.

Furthermore, spray nozzle 36 is preferably stationary, and alsopreferably generates spray 38 without air pressure (e.g., an airlessspray operation). In some embodiments (e.g., in which the can to besprayed is large), spray nozzle 36 may utilize a “lance spray”technique, where spray nozzle 36 may move relative to the can to reachthe far inside end of the can.

In addition, the can 20 itself may be engaged to a rotating mechanism(e.g., a drive roller or belt, and/or a rotatable chuck mount), which isconfigured to rotate the can 20 at a high speed (e.g., about 2,200 rpm)around its longitudinal axis 40, as illustrated by arrows 42. Thisrotation of the can 20 preferably spreads the sprayed coatingcomposition evenly across the entire interior surfaces 30 and 32. As canbe seen in FIG. 2, the flat-fan pattern of spray 38 is not evenlyaligned with the longitudinal axis 40 of the can 20. As such, thepattern of spray 38, as dictated by spray nozzle 36, may benon-homogenous, where the lower portion of spray 38 has a greaterdensity of the coating composition compared to the upper portion ofspray 38.

After the spray coating application, each can 20 may be moved to acuring oven to cure the sprayed coating composition, which is preferablyperformed within about 40 to 200 seconds from the spraying step. Thecuring process is preferably performed in bulk with multiple cans 20arranged together on a continuously moving conveyor belt or track. Thecuring oven preferably heats the cans 20 to a suitable temperature tocure the coating composition, but that is also preferably not too highso as to degrade the coating composition, any other existing coatings oncans 20, and/or the metal materials of cans 20.

Preferred inside spray coating compositions of the present disclosureare capable of being spray applied on an interior of a food or beveragecan (e.g., a 2-piece food or beverage can) to effectively, and evenly,coat the substrate and form a continuous cured coating (e.g., a coatingthat exhibits a suitable initial metal exposure value, therebyindicating that the substrate has been effectively coated and is free ofunsuitable holes or other discontinuities in the coating).

Suitable curing temperatures for the coating composition of the presentdisclosure are greater than about 150° C. (about 300° F.), morepreferably greater than about 165° C. (about 330° F.), and even morepreferably greater than about 180° C. (about 360° F.). In someembodiments, suitable curing temperatures for the coating composition ofthe present disclosure are also less than about 220° C. (about 430° F.),more preferably less than about 205° C. (about 400° F.), and even morepreferably less than about 195° C. (about 380° F.). These temperaturesare based on peak metal temperature measurements of the metal walls ofthe cans 20 as they pass through the curing oven. For example, multiplecans 20 may be grouped together with a test can that is wired withthermocouples to measure the temperatures of one or more portions of themetal walls to ensure the cans 20 are heated enough.

Suitable residence times in the curing oven for the above-discussedtemperatures range from about 40 seconds to about three minutes, morepreferably about one minute to about two minutes. After curing, theresulting cured coatings (e.g., coating 34) may have suitable filmthicknesses for protecting the cans 20 from food or beverage productsthat are subsequently filled into the cans 20.

The desired film thickness for the cured coating may vary depending onthe particular food or beverage to be filled in a given can 20. In someembodiments for the spray coating application (e.g., inside spray forfood or beverage cans), the average film thickness after curing isgreater than about 0.7 milligrams/square-inch (mg/inch²), morepreferably greater than about 0.8 mg/inch², and even more preferablygreater than about 0.9 mg/inch². In these embodiments, the average filmthickness after curing is also less than about 4.0 mg/inch², morepreferably less than about 3.0 mg/inch², and even more preferably lessthan about 2.5 mg/inch².

In some further embodiments, the average film thickness after curingranges from about 0.9 mg/inch² to about 1.1 mg/inch². In other furtherembodiments, the average film thickness after curing ranges from about1.4 mg/inch² to about 1.6 mg/inch². In yet other further embodiments,the average film thickness after curing ranges from about 1.9 mg/inch²to about 2.1 mg/inch².

Alternatively, the coating composition may optionally be applied as acoil coating. During a coil coating application, a continuous coilcomposed of a metal (e.g., steel or aluminum) is coated with the coatingcomposition of the present disclosure. Once coated, the coating coil maybe subjected to a short thermal, ultraviolet, and/or electromagneticcuring cycle, for hardening (e.g., drying and curing) of the coatingcomposition. Coil coatings provide coated metal (e.g., steel and/oraluminum) substrates that can be fabricated into formed articles, suchas two-piece drawn food cans, food can ends, drawn and ironed cans,beverage can ends, and the like.

The coating composition of the present disclosure also offers utility inother coating applications. These additional applications include, butare not limited to, wash coating, sheet coating, and side seam coatings(e.g., food can side seam coatings). Other commercial coatingapplication and curing methods are also envisioned, for example,electrocoating, extrusion coating, laminating, powder coating, and thelike. The coating composition may also be useful in medical or cosmeticpackaging applications, including, for example, on surfaces ofmetered-dose inhalers (“MDIs”), including on drug-contact surfaces.

During the above-discussed curing steps, the aqueous carrier ispreferably vaporized or otherwise dried off from the latex copolymer,allowing the copolymer molecules to cure. If desired, the drying andcuring steps may be combined in a single step or carried out in separatesteps.

Preferred glass transition temperatures for the cured coating of thepresent disclosure (and particularly interior, food-contact coatings)include those greater than about 50° C., more preferably greater thanabout 60° C., even more preferably greater than about 70° C., and insome embodiments, greater than about 80° C. Preferred glass transitiontemperatures for the cured coating include those less than about 120°C., more preferably less than about 115° C., even more preferably lessthan about 110° C., and in some embodiments, less than about 100° C. Theglass transition temperatures can be measured by dynamic mechanicalanalysis (DMA) or differential scanning calorimetry (DSC). Somemulti-unsaturated monomers typically gel when forming homopolymers,which can limit the effectiveness of theoretical calculations using theFlory-Fox Equation.

To further prevent or otherwise reduce coating penetration by anintended food or beverage product, the cured coating is preferablysuitably hydrophobic. For example, the cured coating can have a contactangle with deioinized water greater than about 90, more preferablygreater than about 95, and even more preferably greater than about 100.

The cured coating preferably exhibits desired properties for use as aninside spray coating for food and beverage containers. For example, thecured coating preferably gives a global extraction of less than about 25parts-per-million (ppm), and more preferably less than about 10 ppm, andeven more preferably less than about 1 ppm, pursuant to the GlobalExtraction test below. Additionally, the cured coating preferablyexhibits a metal exposure less than about 5 milliamps (mA), morepreferably less than about 2 mA, and even more preferably less thanabout 1 mA, pursuant to the Initial Metal Exposure test below.

Flexibility is also important so that the coating can deflect with themetal substrate during post-cure fabrication steps (necking and domereformation) and if the can is dropped from a reasonable height duringtransport or use. In some preferred embodiments, the cured coatingshould preferably exhibit a metal exposure less than about 3.5 mA, morepreferably less than about 2.5 mA, and even more preferably less thanabout 1.5 mA, pursuant to the Metal Exposure After Drop Damage testbelow.

Moreover, the coating composition (uncured) should preferably exhibitsubstantially no change (e.g., a change in viscosity, if any, of lessthan 25%, more preferably less than 10%, even more preferably less than5%, and even more preferably less than 1%) in viscosity pursuant to thePot Life Stability test below. Accordingly, the coating composition ofthe present disclosure is particularly suitable for use as an insidespray coating composition for containers configured to retain a varietyof different food or beverage products.

Property Analysis and Characterization Procedures

Various properties and characteristics of the latex emulsions, coatingcompositions, and coatings described herein may be evaluated by varioustesting procedures as described below:

1. Viscosity Test

This test measures the viscosity of a latex emulsion or coatingcomposition for rheological purposes, such as for sprayability and othercoating application properties. The test is performed pursuant to ASTMD1200-88 using a Ford Viscosity Cup #4 at 25° C. The results aremeasured in the units of seconds.

2. Curing Conditions

For beverage inside spray bakes, the curing conditions involvemaintaining the temperature measured at the can dome at 188° C. to 210°C. for 60 seconds. For beverage end coil bakes, the curing conditionsinvolve the use of a temperature sufficient to provide a peak metaltemperature within the specified time (e.g., 10 seconds at 204° C. means10 seconds, in the oven, for example, and a peak metal temperatureachieved of 204° C.). The constructions cited can be evaluated by testsas follows.

3. Initial Metal Exposure

This test method determines the amount of the inside surface of the canthat has not been effectively coated by the sprayed coating. Thisdetermination is made through the use of an electrically conductivesolution (1% NaCl in deionized water). The interior “inside spray”coating is typically applied using a high pressure airless spray. Thefollowing film weights are typically used: 1.0 milligrams per squareinch (“msi”) for a beer can, 1.5 msi for a soda can, and 2.2 msi for acan intended for use in packaging a “hard-to-hold” product.

The coated can is filled with this room-temperature conductive solution,and an electrical probe is attached in contact to the outside of the can(uncoated, electrically conducting). A second probe is immersed in thesalt solution in the middle of the inside of the can.

If any uncoated metal is present on the inside of the can, a current ispassed between these two probes and registers as a value on an LEDdisplay of a suitable measurement apparatus. The LED displays theconveyed currents in milliamps (mA). The current that is passed isdirectly proportional to the amount of metal that has not beeneffectively covered with coating. The goal is to achieve 100% coatingcoverage on the inside of the can, which would result in an LED readingof 0.0 mA. Preferred coatings should give metal exposure values of lessthan 3 mA, more preferred values of less than 2 mA, and even morepreferred values of less than 1 mA. Commercially acceptable metalexposure values are typically less than 2.0 mA on average.

4. Metal Exposure After Drop Damage

Drop damage resistance measures the ability of the coated container toresist cracks after being in conditions simulating dropping of a filledcan. The presence of cracks is measured by passing electrical currentvia an electrolyte solution, as previously described in the InitialMetal Exposure section. A coated container is filled with theelectrolyte solution (1% NaCl in deionized water) and the initial metalexposure is recorded. The electrolyte solution is removed and the can isthen filled with room-temperature tap water. For two-piece “insidespray” beverage cans, the film weights described in the Initial MetalExposure test can be used.

The water-filled can, which does not include a “top” can end, is droppedthrough a cylindrical tube having a 2 and ⅞ inch internal diameter, canbottom down, onto an impact wedge (e.g., an inclined plane angledupwards at 45 degrees). The impact wedge is positioned relative to thetube such that a dent is formed in the rim area where the can bottom endmeets the sidewall (typically referred to as the “chime” of a beveragecan). The water-filled can is dropped through the tube from a24-centimeter height (as measured between the can bottom and the pointof impact on the impact wedge) onto an inclined plane, causing a dent inthe chime area. The can is then turned 180 degrees, and the process isrepeated.

Water is then removed from the can and metal exposure is again measuredas described above. If there is no damage, no change in current (mA)will be observed relative to the Initial Metal Exposure value.Typically, an average of 6 or 12 container runs is recorded. The metalexposures results for before and after the drop are reported as absolutevalues. The lower the milliamp value, the better the resistance of thecoating to drop damage. Preferred coatings should give metal exposurevalues after drop damage of less than 3.5 mA, more preferred values ofless than 2.5 mA, and even more preferred values of less than 1.5 mA.

5. Adhesion

Adhesion testing is performed to assess whether the coating adheres tothe coated substrate. The adhesion test was performed according to ASTMD 3359-Test Method B, using SCOTCH 610 tape, available from 3M Companyof Saint Paul, Minn. Adhesion is generally rated on a scale of 0-10where a rating of “10” indicates no adhesion failure (best), a rating of“9” indicates 90% of the coating remains adhered, a rating of “8”indicates 80% of the coating remains adhered, and so on. Adhesionratings of 10 are typically desired for commercially viable coatings.

6. Blush Resistance

Blush resistance measures the ability of a coating to resist attack byvarious solutions. Typically, blush is measured by the amount ofsolution (e.g., water) absorbed into a coated film. When the filmabsorbs water, it generally becomes cloudy or looks white. Blush isgenerally measured visually using a scale of 0-10 where a rating of “10”indicates no blush (best) and a rating of “0” indicates completewhitening of the film (worst). Blush ratings of 7 or higher aretypically desired for commercially viable coatings, and optimally 9-10.

7. Corrosion Resistance

These tests measure the ability of a coating to resist attack bysolutions of different levels of aggressiveness. Briefly, a givencoating is subjected to a particular solution, as described below, andthen measured for adhesion and blush resistance, each also describedbelow. For each test, a result is given using a scale of 0-10, based onthe Adhesion Resistance, Blush Resistance, and/or Bush AdhesionResistance, where a rating of “10” is best and a rating of “0 is worst.

A. Deionized Water

Deionized water is heated to 82° C. Coated panels are immersed in theheated solution for 30 minutes and then removed, rinsed, and dried.Samples are then evaluated for adhesion and blush, as previouslydescribed.

B. Acetic Acid Solution

A 3% solution of acetic acid (C₂H₄O₂) in deionized water is prepared andheated to 100° C. Coated panels are immersed in the heated solution for30 minutes and then removed, rinsed, and dried. Samples are thenevaluated for adhesion and blush, as previously described.

C. Citric Acid Solution

A 2% solution of citric acid (C₆H₈O₇) in deionized water is prepared andheated while subjected to a pressure sufficient to achieve a solutiontemperature of 121° C. Coated panels are immersed in the heated solutionfor 30 minutes and then removed, rinsed, and dried. Samples are thenevaluated for adhesion and blush, as previously described.

8. Pot Life Stability

The pot life stability of a coating composition is measured by initiallymeasuring its viscosity, and then storing the coating composition at 40°C. for one month. After the one-month period, the viscosity of the agedcoating composition is measured and compared to the initial viscositymeasurement. Substantially no change in viscosity (e.g., a change inviscosity, if any, of less than about 25%, more preferably less thanabout 15%, even more preferably less than about 10%, and even morepreferably less than about 5%) indicates that the coating compositionhas a good pot life stability. In comparison, a significant increase inviscosity (e.g., gelation) indicates that the coating composition haspoor pot life stability.

9. Glass Transition Temperature

Samples for differential scanning calorimetry (“DSC”) testing may beprepared by first applying the liquid resin composition onto aluminumsheet panels. The panels are then baked in a Fisher Isotemp electricoven for 20 minutes at 300° F. (149° C.) to remove volatile materials.After cooling to room temperature, the samples are scraped from thepanels, weighed into standard sample pans and analyzed using thestandard DSC heat-cool-heat method. The samples are equilibrated at −60°C., then heated at 20° C. per minute to 200° C., cooled to −60° C., andthen heated again at 20° C. per minute to 200° C. Glass transitions arecalculated from the thermogram of the last heat cycle. The glasstransition is measured at the inflection point of the transition.

10. Global Extraction

The global extraction test is designed to estimate the total amount ofmobile material that can potentially migrate out of a coating and intofood packed in a coated can. Typically coated substrate is subjected towater or solvent blends under a variety of conditions to simulate agiven end use. Acceptable extraction conditions and media can be foundin 21 CFR § 175.300 paragraphs (d) and (e). The allowable globalextraction limit as defined by the FDA regulation is 50 parts permillion (ppm).

The extraction procedure that can be used in the current invention isdescribed in 21 CFR § 175.300 paragraph (e)(4)(xv) with the followingmodifications to ensure worst-case scenario performance: (1) the alcohol(ethanol) content is increased to 10% by weight, and (2) the filledcontainers are held for a 10-day equilibrium period at 37.8° C. (100°F.). These conditions are per the FDA publication “Guidelines forIndustry” for preparation of Food Contact Notifications.

The coated beverage can is filled with 10% by weight aqueous ethanol andsubjected to pasteurization conditions (65.6° C., 150° F.) for 2 hours,followed by a 10-day equilibrium period at 37.8° C. (100° F.).Determination of the amount of extractives is determined as described in21 CFR § 175.300 paragraph (e) (5), and ppm values are calculated basedon surface area of the can (no end) of 44 square inches with a volume of355 milliliters. Preferred coatings should give global extractionresults of less than 50 ppm, more preferred results of less than 10 ppm,even more preferred results of less than 1 ppm. Most preferably, theglobal extraction results are optimally non-detectable.

In the following embodiment of the present application are summarized:

-   1. A method of forming a coating on a food or beverage container,    the method comprising:    -   receiving a coating composition having an emulsion-polymerized        latex copolymer dispersed in an aqueous carrier, wherein the        emulsion-polymerized latex polymer is a reaction product of        monomers comprising:        -   one or more first ethylenically-unsaturated monomers each            having one or more ethylenically-unsaturated groups; and        -   one or more styrene offset monomers comprising:            -   (i) one or more ethylenically-unsaturated, polycyclic                monomers;            -   (ii) one or more ethylenically-unsaturated, monocyclic                monomers each having a ring structure with 3-5 atoms in                the ring; or            -   combinations thereof, wherein a combined concentration                of (i) and (ii) constitutes at least about 10% by weight                of the monomers used to produce the emulsion-polymerized                latex copolymer;        -   wherein the monomers used to produce the            emulsion-polymerized latex copolymer are substantially free            of BPA, PVC, and styrene; and    -   applying the coating composition to a substrate prior to or        after forming the substrate into a food or beverage container,        or a portion thereof.-   2. The method of item 1, wherein applying the coating composition to    the substrate comprises:    -   spraying the provided coating composition onto an interior        surface of the food or beverage container; and    -   curing the sprayed coating composition to substantially remove        the aqueous carrier, and provide the coating on the interior        surface of the food or beverage container.-   3. The method of item 2, wherein the coating composition has an    average viscosity ranging from about 5 seconds to about 40 seconds,    pursuant to the Viscosity Test.-   4. The method of item 3, wherein the average viscosity of the    coating composition ranges from about 15 seconds to about 25    seconds.-   5. The method of any preceding item, wherein the coating composition    has a resin solids content ranging from about 10% by weight to about    30% by weight, based on a total weight of the coating composition;-   6. The method of any preceding item, wherein the one or more first    ethylenically-unsaturated monomers are each substantially free of    cyclic groups.-   7. The method of any preceding item, wherein the one or more first    ethylenically-unsaturated monomers comprise:    -   one or more ethylenically-unsaturated, acid-functional monomers;    -   one or more non-cyclic (meth)acrylates; or    -   combinations thereof.-   8. The method of item 7, wherein the one or more    ethylenically-unsaturated, acid-functional monomers constitute at    least 1% by weight of the emulsion-polymerized latex compolymer,    based on the total weight of the monomers used to produce the    emulsion-polymerized latex copolymer.-   9. The method of item 8, wherein the one or more    ethylenically-unsaturated, acid-functional monomers constitute at    least 3% by weight of the emulsion-polymerized latex compolymer,    based on the total weight of the monomers used to produce the    emulsion-polymerized latex copolymer.-   10. The method of item 9, wherein the concentration of the one or    more ethylenically-unsaturated, acid-functional monomers ranges from    5% by weight to 20% by weight, based on the total weight of the    monomers used to produce the emulsion-polymerized latex copolymer.-   11. The method of any one of items 7-10, wherein the one or more    non-cyclic (meth)acrylates have a concentration ranging from 10% by    weight to 70% by weight, based on the total weight of the monomers    used to produce the emulsion-polymerized latex copolymer.-   12. The method of item 11, wherein the concentration of the one or    more non-cyclic (meth)acrylates ranges from about 20% by weight to    about 60% by weight, based on the total weight of the monomers used    to produce the emulsion-polymerized latex copolymer.-   13. The method of item 12, wherein the concentration of the one or    more non-cyclic (meth)acrylates ranges from about 30% by weight to    about 50% by weight, based on the total weight of the monomers used    to produce the emulsion-polymerized latex copolymer.-   14. The method of any one of items 7-13, wherein the one or more    non-cyclic (meth)acrylates comprise a hydroxy-functional non-cyclic    (meth)acrylate.-   15. The method of any one of items 7-14, wherein the one or more    first ethylenically-unsaturated monomers further comprise one or    more polymerizable surfactants.-   16. The method of any one of items 7-15, wherein the one or more    first ethylenically-unsaturated monomers further comprise one or    more multi-functional monomers.-   17. The method of item 16, wherein the one or more multi-functional    monomers comprises a monomer have two or more    ethylenically-unsaturated groups.-   18. The method of any one of items 1-17, wherein the combined    concentration of (i) and (ii) constitutes at least 20% by weight of    the monomers used to produce the emulsion-polymerized latex    copolymer.-   19. The method of item 18, wherein the combined concentration of (i)    and (ii) constitutes at least 30% by weight of the monomers used to    produce the emulsion-polymerized latex copolymer.-   20. The method of any preceding item, wherein the one or more    ethylenically-unsaturated, polycyclic monomers constitute at least    10% by weight of the monomers used to produce the    emulsion-polymerized latex copolymer.-   21. The method of item 20, wherein the one or more    ethylenically-unsaturated, polycyclic monomers constitute at least    20% by weight of the monomers used to produce the    emulsion-polymerized latex copolymer.-   23. The method of item 21, wherein the one or more    ethylenically-unsaturated, polycyclic monomers constitute at least    30% by weight of the monomers used to produce the    emulsion-polymerized latex copolymer.-   24. The method of any preceding item, wherein the one or more    ethylenically-unsaturated, monocyclic monomers constitute at least    10% by weight of the monomers used to produce the    emulsion-polymerized latex copolymer.-   25. The method of item 24, wherein the one or more    ethylenically-unsaturated, monocyclic monomers constitute at least    20% by weight of the monomers used to produce the    emulsion-polymerized latex copolymer.-   26. The method of item 25, wherein the one or more    ethylenically-unsaturated, monocyclic monomers constitute at least    30% by weight of the monomers used to produce the    emulsion-polymerized latex copolymer.-   27. The method of any preceding item, and further comprising one or    more ethylenically-unsaturated, monocyclic monomers each having a    ring structure with 6 or more atoms in the ring.-   28. The method of any preceding item, wherein the one or more    ethylenically-unsaturated, polycyclic monomers are selected from the    group consisting of isobornyl (meth)acrylate), norbornane    (meth)acrylate, norbornene (meth)acrylate, norbornadiene,    tricyclodecenyl (meth)acrylate, isosorbide (metha)crylate,    tricyclodecane (meth)acrylate, bicyclo[4.4.0]decane (meth)acrylate,    vinyl variations thereof, and mixtures thereof.-   29. The method of any preceding item, wherein the one or more    ethylenically-unsaturated, polycyclic monomers comprise polycyclic    groups that are derived from plant based materials.-   30. The method of any preceding item, wherein the coating has a    glass transition temperature greater than about 50° C.-   31. The method of item 30, wherein the glass transition temperature    of the coating ranges from about 60° C. to about 120° C.-   32. The method of item 31, wherein the glass transition temperature    of the coating ranges from about 80° C. to about 110° C.-   33. The method of any preceding item, wherein the coating    composition further includes a crosslinking agent.-   34. The method of any preceding item, wherein the food or beverage    container comprises a two-piece aluminum beverage can.-   35. The method of any preceding item, wherein the coating    composition exhibits substantially no change in viscosity pursuant    to the Pot Life Stability test (e.g., a change in viscosity, if any,    of less than about 25%, more preferably less than about 15%, even    more preferably less than about 10%, and even more preferably less    than about 5%).-   36. The method of any preceding item, wherein the coating gives a    global extraction of less than 10 parts-per-million, pursuant to the    Global Extraction test.-   37. The method of item 36, wherein the coating gives a global    extraction of less than 1 part-per-million, pursuant to the Global    Extraction test.-   38. The method of any preceding item, wherein the coating    composition is substantially free of halogenated compounds.-   39. The method of any preceding item, wherein the coating    composition is spray applied onto an interior surface of an aluminum    beverage can including a body portion and a bottom end portion, and    where the cured coating has a coating thickness ranging of from    about 0.7 milligrams/square-inch (mg/inch²) to about 2.5 mg/inch².-   40. The method of any preceding item, wherein the monomers used to    produce the emulsion-polymerized latex copolymer are substantially    free of oxirane groups.-   41. An article comprising a food or beverage container, or a portion    thereof, including:    -   a metal substrate; and    -   an inside spray coating disposed on at least a portion of the        metal substrate, wherein the coating is produced from an        inside-spray coating composition having an emulsion-polymerized        latex copolymer that is a reaction product of monomers        comprising:        -   one or more first ethylenically-unsaturated monomers each            having one or more ethylenically-unsaturated groups; and        -   one or more styrene offset monomers comprising:            -   (i) one or more ethylenically-unsaturated, polycyclic                monomers;            -   (ii) one or more ethylenically-unsaturated, monocyclic                monomers each having a ring structure with 3-5 atoms in                the ring; or            -   combinations thereof,            -   wherein a combined concentration of (i) and (ii)                constitutes at least about 10% by weight of the monomers                used to produce the emulsion-polymerized latex                copolymer;        -   wherein the monomers used to produce the            emulsion-polymerized latex copolymer are substantially free            of BPA, PVC, halogenated monomer, and styrene.-   42. The article of item 41, wherein the one or more one or more    first ethylenically-unsaturated monomers comprise:    -   one or more ethylenically-unsaturated, acid-functional monomers;    -   one or more non-cyclic (meth)acrylates; or    -   combinations thereof-   43. The article of item 42, wherein the one or more    ethylenically-unsaturated, acid-functional monomers constitute at    least 1% by weight of the emulsion-polymerized latex copolymer,    based on the total weight of the monomers used to produce the    emulsion-polymerized latex copolymer.-   44. The article of item 43, wherein the one or more    ethylenically-unsaturated, acid-functional monomers constitute at    least 3% by weight of the emulsion-polymerized latex compolymer,    based on the total weight of the monomers used to produce the    emulsion-polymerized latex copolymer.-   45. The article of item 44, wherein the concentration of the one or    more ethylenically-unsaturated, acid-functional monomers ranges from    5% by weight to 20% by weight, based on the total weight of the    monomers used to produce the emulsion-polymerized latex copolymer.-   46. The article of any one of items 42-45, wherein the one or more    non-cyclic (meth)acrylates have a concentration ranging from 10% by    weight to 70% by weight, based on the total weight of the monomers    used to produce the emulsion-polymerized latex copolymer.-   47. The article of item 46, wherein the concentration of the one or    more non-cyclic (meth)acrylates ranges from about 20% by weight to    about 60% by weight, based on the total weight of the monomers used    to produce the emulsion-polymerized latex copolymer.-   48. The article of item 47, wherein the concentration of the one or    more non-cyclic (meth)acrylates ranges from about 30% by weight to    about 50% by weight, based on the total weight of the monomers used    to produce the emulsion-polymerized latex copolymer.-   49. The article of any one of items 42-48, wherein the one or more    non-cyclic (meth)acrylates comprise a hydroxy-functional    non-aromatic (meth)acrylate.-   50. The article of any one of items 42-49, wherein the one or more    first ethylenically-unsaturated monomers further comprise one or    more polymerizable surfactants.-   51. The article of any one of items 42-50, wherein the one or more    first ethylenically-unsaturated monomers further comprise one or    more multi-functional monomers.-   52. The article of item 51, wherein the one or more multi-functional    monomers comprises a monomer have two or more    ethylenically-unsaturated groups.-   53. The article of any one of items 41-52, wherein the combined    concentration of (i) and (ii) constitutes at least 20% by weight of    the monomers used to produce the emulsion-polymerized latex    copolymer.-   54. The article of item 53, wherein the combined concentration    of (i) and (ii) constitutes at least 30% by weight of the monomers    used to produce the emulsion-polymerized latex copolymer.-   55. The article of any one of items 41-54, wherein the one or more    ethylenically-unsaturated, polycyclic monomers constitute at least    10% by weight of the monomers used to produce the    emulsion-polymerized latex copolymer.-   56. The article of item 55, wherein the one or more    ethylenically-unsaturated, polycyclic monomers constitute at least    20% by weight of the monomers used to produce the    emulsion-polymerized latex copolymer.-   57. The article of item 56, wherein the one or more    ethylenically-unsaturated, polycyclic monomers constitute at least    30% by weight of the monomers used to produce the    emulsion-polymerized latex copolymer.-   58. The article of any one of items 41-57, wherein the one or more    ethylenically-unsaturated, monocyclic monomers constitute at least    10% by weight of the monomers used to produce the    emulsion-polymerized latex copolymer.-   59. The article of item 58, wherein the one or more    ethylenically-unsaturated, monocyclic monomers constitute at least    20% by weight of the monomers used to produce the    emulsion-polymerized latex copolymer.-   60. The article of item 59, wherein the one or more    ethylenically-unsaturated, monocyclic monomers constitute at least    30% by weight of the monomers used to produce the    emulsion-polymerized latex copolymer.-   61. The article of any one of items 41-60, and further comprising    one or more ethylenically-unsaturated, monocyclic monomers each    having a ring structure with 6 or more atoms in the ring.-   62. The article of any one of items 41-61, wherein the coating has a    glass transition temperature greater than about 50° C.-   63. The article of item 62, wherein the glass transition temperature    of the coating ranges from about 60° C. to about 120° C.-   64. The article of item 63, wherein the glass transition temperature    of the coating ranges from about 80° C. to about 110° C.-   65. The article of any one of items 41-64, wherein the coating    composition further includes a crosslinking agent.-   66. The article of any one of items 41-65, wherein the coating    composition is substantially free of halogenated compounds.-   67. The article of any one of items 41-66, wherein the cured coating    has a coating thickness ranging of from about 0.7    milligrams/square-inch (mg/inch²) to about 2.5 mg/inch².-   68. The article of any one of items 41-67, wherein the one or more    ethylenically-unsaturated, polycyclic monomers are selected from the    group consisting of isobomyl (meth)acrylate), norbornane    (meth)acrylate, norbornene (meth)acrylate, norbornadiene,    tricyclodecenyl (meth)acrylate, isosorbide (metha)crylate,    tricyclodecane (meth)acrylate, bicyclo[4.4.0]decane (meth)acrylate,    vinyl variations thereof, and mixtures thereof.-   69. The article of any one of items 41-67, wherein the one or more    ethylenically-unsaturated, polycyclic monomers comprise polycyclic    groups that are derived from plant based materials.-   70. The article of any one of items 41-69, wherein the monomers used    to produce the emulsion-polymerized latex copolymer are    substantially free of oxirane groups.-   71. The article of any one of items 41-69, wherein the monomers used    to produce the emulsion-polymerized latex copolymer are    substantially free of glycidyl methacrylate and glycidyl acrylate.-   72. An inside spray coating composition comprising:    -   an aqueous carrier; and    -   an emulsion-polymerized latex copolymer dispersed in the aqueous        carrier, and comprising:        -   one or more ethylenically-unsaturated monomers each having            one or more ethylenically-unsaturated groups; and        -   one or more styrene offset monomers comprising:            -   (i) one or more ethylenically-unsaturated, polycyclic                monomers;            -   (ii) one or more ethylenically-unsaturated, monocyclic                monomers each having a ring structure with 3-5 atoms in                the ring; or combinations thereof,            -   wherein a combined concentration of (i) and (ii)                constitutes at least about 10% by weight of the monomers                used to produce the emulsion-polymerized latex                copolymer;        -   wherein the monomers used to produce the            emulsion-polymerized latex copolymer are substantially free            of BPA, PVC, halogenated monomers, and styrene;    -   wherein the coating composition has an average viscosity ranging        from about 5 seconds to about 40 seconds, pursuant to the        Viscosity Test; and    -   wherein the coating composition has a resin solids content        ranging from about 10% by weight to about 30% by weight, based        on a total weight of the coating composition.-   73. The coating composition of item 72, wherein the average    viscosity of the coating composition ranges from about 15 seconds to    about 25 seconds.-   74. The coating composition of any one of items 72-73, wherein the    one or more ethylenically-unsaturated monomers comprise:    -   one or more ethylenically-unsaturated, acid-functional monomers;    -   one or more non-cyclic (meth)acrylates; or    -   combinations thereof.-   75. The coating composition of item 74, wherein the one or more    ethylenically-unsaturated, acid-functional monomers constitute at    least 1% by weight of the emulsion-polymerized latex compolymer,    based on the total weight of the monomers used to produce the    emulsion-polymerized latex copolymer.-   76. The coating composition of item 75, wherein the one or more    ethylenically-unsaturated, acid-functional monomers constitute at    least 3% by weight of the emulsion-polymerized latex compolymer,    based on the total weight of the monomers used to produce the    emulsion-polymerized latex copolymer.-   77. The coating composition of item 76, wherein the concentration of    the one or more ethylenically-unsaturated, acid-functional monomers    ranges from 5% by weight to 20% by weight, based on the total weight    of the monomers used to produce the emulsion-polymerized latex    copolymer.-   78. The coating composition of any one of items 74-77, wherein the    one or more non-cyclic (meth)acrylates have a concentration ranging    from 10% by weight to 70% by weight, based on the total weight of    the monomers used to produce the emulsion-polymerized latex    copolymer.-   79. The coating composition of item 78, wherein the concentration of    the one or more non-cyclic (meth)acrylates ranges from about 20% by    weight to about 60% by weight, based on the total weight of the    monomers used to produce the emulsion-polymerized latex copolymer.-   80. The coating composition of item 79, wherein the concentration of    the one or more non-cyclic (meth)acrylates ranges from about 30% by    weight to about 50% by weight, based on the total weight of the    monomers used to produce the emulsion-polymerized latex copolymer.-   81. The coating composition of any one of items 74-80, wherein the    one or more non-cyclic (meth)acrylates comprise a hydroxy-functional    non-cyclic (meth)acrylate.-   82. The coating composition of any one of items 74-81, wherein the    one or more first ethylenically-unsaturated monomers further    comprise one or more polymerizable surfactants.-   83. The coating composition of any one of items 74-82, wherein the    one or more first ethylenically-unsaturated monomers further    comprise one or more multi-functional monomers.-   84. The coating composition of item 83, wherein the one or more    multi-functional monomers comprises a monomer have two or more    ethylenically-unsaturated groups.-   85. The coating composition of any one of items 72-84, wherein the    combined concentration of (i) and (ii) constitutes at least 20% by    weight of the monomers used to produce the emulsion-polymerized    latex copolymer.-   86. The coating composition of item 85, wherein the combined    concentration of (i) and (ii) constitutes at least 30% by weight of    the monomers used to produce the emulsion-polymerized latex    copolymer.-   87. The coating composition of any one of items 72-86, wherein the    one or more ethylenically-unsaturated, polycyclic monomers    constitute at least 10% by weight of the monomers used to produce    the emulsion-polymerized latex copolymer.-   88. The coating composition of item 87, wherein the one or more    ethylenically-unsaturated, polycyclic monomers constitute at least    20% by weight of the monomers used to produce the    emulsion-polymerized latex copolymer.-   89. The coating composition of item 88, wherein the one or more    ethylenically-unsaturated, polycyclic monomers constitute at least    30% by weight of the monomers used to produce the    emulsion-polymerized latex copolymer.-   90. The coating composition of any one of items 72-89, wherein the    one or more ethylenically-unsaturated, monocyclic monomers    constitute at least 10% by weight of the monomers used to produce    the emulsion-polymerized latex copolymer.-   91. The coating composition of item 90, wherein the one or more    ethylenically-unsaturated, monocyclic monomers constitute at least    20% by weight of the monomers used to produce the    emulsion-polymerized latex copolymer.-   92. The coating composition of item 91, wherein the one or more    ethylenically-unsaturated, monocyclic monomers constitute at least    30% by weight of the monomers used to produce the    emulsion-polymerized latex copolymer.-   93. The coating composition of any one of items 72-92, and further    comprising one or more ethylenically-unsaturated, monocyclic    monomers each having a ring structure with 6 or more atoms in the    ring.-   94. The coating composition of any one of items 72-93, wherein the    one or more ethylenically-unsaturated, polycyclic monomers are    selected from the group consisting of isobornyl (meth)acrylate),    norbornane (meth)acrylate, norbornene (meth)acrylate, norbornadiene,    tricyclodecenyl (meth)acrylate, isosorbide (metha)crylate,    tricyclodecane (meth)acrylate, bicyclo[4.4.0]decane (meth)acrylate,    vinyl variations thereof, and mixtures thereof.-   95. The coating composition of any one of items 72-93, wherein the    one or more ethylenically-unsaturated, polycyclic monomers comprise    polycyclic groups that are derived from plant based materials.-   96. The coating composition of any one of items 72-95, wherein the    coating composition further includes a crosslinking agent.-   97. The coating composition of any one of items 72-96, wherein the    coating composition exhibits substantially no change in viscosity    pursuant to the Pot Life Stability test (e.g., a change in    viscosity, if any, of less than about 25%, more preferably less than    about 15%, even more preferably less than about 10%, and even more    preferably less than about 5%).-   98. The coating composition of any one of items 72-97, wherein the    coating composition is substantially free of halogenated compounds.-   99. The coating composition of any one of items 72-98, wherein the    monomers used to produce the emulsion-polymerized latex copolymer    are substantially free of oxirane groups.

EXAMPLES

The present disclosure is more particularly described in the followingexamples that are intended as illustrations only, since numerousmodifications and variations within the scope of the present disclosurewill be apparent to those skilled in the art.

Coating Composition CC1

A coating composition CC1 was prepared using a two-stage polymerizationprocess. For the first-stage polymerization, deionized water, apolymerizable surfactant monomer, and an organic acid catalyst wereadded to a reactor, which was then heated under nitrogen sparge to 80°C. with agitation. Once equilibrium temperature was reached, aninitiator solution and the first-stage monomers were introduced to thesurfactant dispersion in the reactor continuously over a 75-minuteduration while the reactor was maintained under nitrogen sparge at thetemperature of 80° C. with agitation.

The initiator solution included ammonium persulphate and deionizedwater. The first-stage monomers are listed below in Table 1, andincluded an aromatic methacrylate instead of styrene. After all of theinitiator solution and the first-stage monomers were added, the reactorwas held at the temperature of 80° C. under agitation for an additional30 minutes to complete the first-stage emulsion polymerization, therebyproducing an in situ latex emulsion having the first-stage copolymers.These first-stage copolymers included chain segments of thepolymerizable surfactant monomer, and carboxylic acid groups.

A portion of the carboxylic acid groups of the resulting first-stagecopolymers was then neutralized for water-dispersibility purposes. Thisincluded introducing dimethylethanol amine (DMEA) and deionized waterover a period of 60 minutes. After neutralization, an inhibitor solutionof phenothiazine and butyl glycol was added to the reactor to inhibitfurther polymerization. The in situ latex emulsion was agitated at thetemperature of 80° C. for an additional five minutes.

Glycidyl methacrylate was then introduced to the reactor to react withsome of the remaining carboxylic acid groups of the first-stagecopolymers using a step-growth reaction. After the glycidyl methacrylatewas introduced, the reactor was agitated at the temperature of 80° C.for three hours to complete the step-growth reaction. During thestep-growth reaction, the oxirane groups of the glycidyl methacrylatereacted with the carboxylic acid groups of the first-stage copolymers tograft the glycidyl methacrylate chains to the first-stage copolymers viaester linkages. This produced linkage groups characterized as pendantester segments with terminated with vinyl groups.

After the linkage group grafting step was completed, a redox solutionwas introduced to the reactor, which included ferrous sulphateheptahydrate, tertioamyl hydroperoxide, and deionized water. Then asecond initiator solution and the second-stage monomers were introducedto the reactor continuously over a 75-minute duration while the reactorwas maintained under nitrogen sparge at the temperature of 80° C. withagitation.

The second initiator solution included isoascorbic acid, dimethylethanolamine (DMEA), and deionized water. The second-stage monomers are alsolisted below in Table 1, and included polycyclic methacrylate instead ofstyrene. During the second-stage polymerization, after all of the secondinitiator solution and the second-stage monomers were added, the reactorwas held at the temperature of 80° C. under agitation for an additional45 minutes.

Then a spike of the initiator and redox solutions was added to reducethe level of free monomers. The spike included 0.001 parts of ferroussulphate heptahydrate, 0.3 parts of tertioamyl hydroperoxide, 0.2 partsof isoascorbic acid, 0.12 parts of DMEA, and 10 parts of deionizedwater. The reactor was maintained under nitrogen sparge at thetemperature of 80° C. with agitation for an additional two hours tocomplete the second-stage emulsion polymerization, thereby producing alatex emulsion of the present disclosure.

After the second-stage polymerization was completed, the reactor wasslowly cooled down to 40° C. and filtered to collect the resulting latexemulsion, where no coagulum was visibly observable. The resulting latexemulsion had a total solids content of 33.0% by weight. The resultinglatex emulsion copolymers included monomer concentrations as listedbelow in Table 1.

TABLE 1 Percent by weight First-Stage Monomers and Linkage MonomersPolyermizable Surfactant (Reasoap SR1025) 2.8 Benzyl Methacrylate 52.8Methacrylic Acid 19.4 Isobornyl Acrylate 17.6 Hydroxyethyl Methacrylate(HEMA) 3.5 Glycidyl Methacrylate (GMA) - Linkage Monomers 3.9Second-Stage Monomers Benzyl Methacrylate 44.8 Glycidyl Methacrylate(GMA) 18.3 Ethyl Acrylate 17.4 Isobornyl Acrylate 14.9 HydroxyethylMethacrylate (HEMA) 4.6 Total Monomers First-Stage Monomers 51.1 LinkageMonomers 2.1 Second-Stage Monomers 46.8

The resulting latex emulsion was then diluted with a solution ofdeionized water and organic solvents to reach a viscosity between 15 and25 seconds based on the Viscosity Test. This resulted in the coatingcomposition CC1, which did not include any external crosslinker.

The complete disclosures of the patents, patent documents, andpublications cited herein are incorporated by reference to the extentthat they do not conflict with the present disclosure. Although thepresent disclosure has been described with reference to preferredembodiments, workers skilled in the art will recognize that changes maybe made in form and detail without departing from the spirit and scopeof the disclosure.

The invention claimed is:
 1. A method of forming a coating on a food orbeverage container, the method comprising: receiving a coatingcomposition having an emulsion-polymerized latex copolymer dispersed inan aqueous carrier, wherein the emulsion-polymerized latex copolymer isa reaction product of monomers comprising: one or more firstethylenically-unsaturated monomers each having one or moreethylenically-unsaturated groups; and one or more styrene offsetmonomers comprising: (i) one or more ethylenically-unsaturated,polycyclic monomers; (ii) one or more ethylenically-unsaturated,monocyclic monomers each having a ring structure with 3-5 atoms in thering; or combinations thereof, wherein a combined concentration of (i)and (ii) constitutes at least about 10% by weight of the monomers usedto produce the emulsion-polymerized latex copolymer; wherein themonomers used to produce the emulsion-polymerized latex copolymer aresubstantially free of BPA, PVC, halogenated monomers, and styrene; andapplying the coating composition to a substrate prior to or afterforming the substrate into a food or beverage container, or a portionthereof.
 2. The method of claim 1, wherein applying the coatingcomposition to the substrate comprises: spraying the coating compositiononto an interior surface of the food or beverage container; and curingthe sprayed coating composition to substantially remove the aqueouscarrier, and provide the coating on the interior surface of the food orbeverage container.
 3. The method of claim 2, wherein the averageviscosity of the coating composition ranges from about 15 seconds toabout 25 seconds, pursuant to the Viscosity Test.
 4. The method of claim2, wherein the one or more first ethylenically-unsaturated monomers areeach substantially free of cyclic groups.
 5. The method of claim 2,wherein the one or more first ethylenically-unsaturated monomerscomprise: one or more ethylenically-unsaturated, acid-functionalmonomers; one or more non-cyclic (meth)acrylates; or combinationsthereof.
 6. The method of claim 5, wherein the one or moreethylenically-unsaturated, acid-functional monomers constitute at least3% by weight of the emulsion-polymerized latex copolymer, based on thetotal weight of the monomers used to produce the emulsion-polymerizedlatex copolymer.
 7. The method of claim 5, wherein the one or morenon-cyclic (meth)acrylates have a concentration ranging from 10% byweight to 70% by weight, based on the total weight of the monomers usedto produce the emulsion-polymerized latex copolymer.
 8. The method ofclaim 7, wherein the concentration of the one or more non-cyclic(meth)acrylates ranges from about 20% by weight to about 60% by weight,based on the total weight of the monomers used to produce theemulsion-polymerized latex copolymer.
 9. The method of claim 8, whereinthe concentration of the one or more non-cyclic (meth)acrylates rangesfrom about 30% by weight to about 50% by weight, based on the totalweight of the monomers used to produce the emulsion-polymerized latexcopolymer.
 10. The method of claim 2, wherein the one or more firstethylenically-unsaturated monomers further comprise one or morepolymerizable surfactants.
 11. The method of claim 2, wherein the one ormore first ethylenically-unsaturated monomers further comprise one ormore multi-functional monomers having two or moreethylenically-unsaturated groups.
 12. The method of claim 2, wherein theone or more ethylenically-unsaturated, polycyclic monomers constitute atleast 10% by weight of the monomers used to produce theemulsion-polymerized latex copolymer.
 13. The method of claim 2, whereinthe one or more ethylenically-unsaturated, monocyclic monomersconstitute at least 10% by weight of the monomers used to produce theemulsion-polymerized latex copolymer.
 14. The method of claim 2, whereinthe coating has a glass transition temperature greater than 50° C. 15.The method of claim 2, wherein the coating gives a global extraction ofless than 10 parts-per-million, pursuant to the Global Extraction test,and wherein the coating composition is substantially free of halogenatedcompounds.
 16. The method of claim 2, wherein the coating composition isspray applied onto an interior surface of an aluminum beverage canincluding a body portion and a bottom end portion, and where the curedcoating has a coating thickness ranging of from about 0.7milligrams/square-inch (mg/inch²) to about 2.5 mg/inch².
 17. The methodof claim 1, wherein the coating composition has a resin solids contentranging from about 10% by weight to about 30% by weight, based on atotal weight of the coating composition.
 18. The method of claim 1,wherein the concentration of the one or more ethylenically-unsaturated,acid-functional monomers ranges from 5% by weight to 20% by weight,based on the total weight of the monomers used to produce theemulsion-polymerized latex copolymer.
 19. The method of claim 1, whereinthe combined concentration of (i) and (ii) constitutes at least 30% byweight of the monomers used to produce the emulsion-polymerized latexcopolymer.
 20. The method of claim 1, wherein the one or moreethylenically-unsaturated, polycyclic monomers constitute at least 30%by weight of the monomers used to produce the emulsion-polymerized latexcopolymer.
 21. The method of claim 1, wherein the one or moreethylenically-unsaturated, polycyclic monomers are selected from thegroup consisting of isobornyl (meth)acrylate), norbornane(meth)acrylate, norbornene (meth)acrylate, norbornadiene,tricyclodecenyl (meth)acrylate, isosorbide (meth)acrylate,tricyclodecane (meth)acrylate, bicyclo[4.4.0]decane (meth)acrylate,vinyl variations thereof, and mixtures thereof.
 22. The method of claim1, wherein the glass transition temperature of the coating ranges fromabout 60° C. to about 120° C.
 23. The method of claim 1, wherein thecoating composition exhibits a change in viscosity, if any, of less thanabout 25% pursuant to the Pot Life Stability test.
 24. An articlecomprising a food or beverage container, or a portion thereof,including: a metal substrate; and an inside spray coating disposed on atleast a portion of the metal substrate, wherein the coating is producedfrom an inside-spray coating composition having an emulsion-polymerizedlatex copolymer that is a reaction product of monomers comprising: oneor more first ethylenically-unsaturated monomers each having one or moreethylenically-unsaturated groups; and one or more styrene offsetmonomers comprising: (i) one or more ethylenically-unsaturated,polycyclic monomers; (ii) one or more ethylenically-unsaturated,monocyclic monomers each having a ring structure with 3-5 atoms in thering; or combinations thereof, wherein a combined concentration of (i)and (ii) constitutes at least about 10% by weight of the monomers usedto produce the emulsion-polymerized latex copolymer; wherein themonomers used to produce the emulsion-polymerized latex copolymer aresubstantially free of BPA, PVC, halogenated monomers, and styrene. 25.An inside spray coating composition comprising: an aqueous carrier; andan emulsion-polymerized latex copolymer dispersed in the aqueouscarrier, and comprising: one or more ethylenically-unsaturated monomerseach having one or more ethylenically-unsaturated groups; and one ormore styrene offset monomers comprising: (i) one or moreethylenically-unsaturated, polycyclic monomers; (ii) one or moreethylenically-unsaturated, monocyclic monomers each having a ringstructure with 3-5 atoms in the ring; or combinations thereof, wherein acombined concentration of (i) and (ii) constitutes at least about 10% byweight of the monomers used to produce the emulsion-polymerized latexcopolymer; wherein the monomers used to produce the emulsion-polymerizedlatex copolymer are substantially free of BPA, PVC, halogenatedmonomers, and styrene; wherein the coating composition has an averageviscosity ranging from about 5 seconds to about 40 seconds, pursuant tothe Viscosity Test; and wherein the coating composition has a resinsolids content ranging from about 10% by weight to about 30% by weight,based on a total weight of the coating composition.